Should Network Cables Be Replaced? 524
Jyms writes "As technology changes, so hubs routers and switches are upgraded, but does the cabling need replacing, and if so, how often? Coax gave way to CAT 5 and CAT 5e replaced that. If you are running a 100Mbit/s network on old CAT 5, can that affect performance? Do CAT 5(e) cables get old?"
Cat6 (Score:5, Informative)
Also, there is cat6 cables out with better specs and can handle at least up 10gb/sec.
Outdoor or indoor? (Score:2, Informative)
I'd consider replacing cables exposed to the elements or extreme temperatures (+/- 40 from room temp) every 10 years if you have the budget. Perhaps 2% of your cabling? Drawing from zero experience though.
Re:Cat6 (Score:4, Informative)
"get old"? (Score:5, Informative)
I'm not sure what would "get old" exactly. It's insulated copper, so I think it should be good so long as they aren't damaged. If anyone knows better, feel free to correct me.
If you want to be sure, though, test them. Transfer files over your network. If the connection is bad, you can try replacing the cable and see if that works. But the fact that Cat6 is out doesn't mean you have to rush out and replace all your CAT5e cables, especially if you're only dealing with normal 100mbps connections. But I use CAT5e for 1gbps connections, and that seems to work fine.
Re:Cat6 (Score:5, Informative)
CAT6 is a PITA to use residentially. It is much stiffer, due to a "coffee stirrer" embedded in the middle, and doesn't bend well at all. I just downgraded from CAT6 to CAT5e for hooking portables up to my GbE LAN, just because of how unwieldy CAT6 was.
The CAT6 plugs can also be a problem -- they are by necessity slightly thicker (the strands alternate in height when crimped), which can make them a tough fit for some devices.
Re:"get old"? (Score:3, Informative)
Depending on the exact insulation and the environment (see a previous post regarding outdoor cabling), the insulation could degrade with age.
Also, the physical geometry of the cabling is important for high speed networks. If the cable gets moved around frequently, it could degrade to the point where it no longer works.
There is of course the whole upgradability thing - Cat5 is good enough for 100M, and 5e is good enough for gigabit, but what if a few years down the line you want to go 10GbE? It seems outlandishly fast now, but it's around a 5-8 year cycle between Ethernet generations. What's standard now (GbE) for new installations will be "old hat" in 5-8 years.
It's a lot easier to upgrade networking equipment at the endpoints than to upgrade cabling runs.
Re:Gold plated baby! (Score:2, Informative)
Simple answer.. (Score:2, Informative)
No.
I'll be here all week.
Bad Connectors (Score:3, Informative)
We had a contractor wire our office and had no problems until we started using roaming profiles. A few of the connection terminators were bad and only allowed a 1mb/s connection. The computers that had these problems normally only transfered a text files from the server, or surfed the internet and weren't really using more than that bandwidth anyway. So, with large file copies associated with roaming profiles, we finally found the problem. At that point, I distrusted the contractors work and had every connection redone (40 total) and retested to the full 1000mbs our network actually supported.
So my suggestion is this. Unless someone kicks the cable every day, there isn't much to go wrong. Monitor for abnormally high number of collisions on one port, and yearly perform throughput tests.
Test it... (Score:4, Informative)
Cables don't get "old" by themselves, but they might have been installed incorrectly from the start (too tight bending, swapped pairs/cables, twisted pairs separated for a longer distance, shields not connected properly, grounding done wrong). Furthermore mechanical stress (too much work being done on a patch panel over the course of several years, cables pulled hard while moving racks, ...) might have damaged parts of the cabling.
To cut a long story short: Properly done CAT5 should be good enough for Gigabit, but often what's called CAT5 works well for 100 Mbit networks even though it doesn't meet the specs.
Get a decent LAN tester (not just two computers, using "ping") that prints out attenuation, crosstalk and all the other things... and preferably tells you what "category" your cabling still is compatible with. Replace all the stuff that's out of spec. Then you have hard numbers you can rely on should you ever ponder if your local network infrastructure can handle 100M/1G/10G bit/s. Everything else is guesswork.
Re:"get old"? (Score:3, Informative)
Re:Cat6 (Score:5, Informative)
Foresight certainly helps. I wired my home twelve years ago with 622 Mbit/s teflon-coated copper twisted-pair ATM wiring. It was the best I could easily (and cheaply since it was left over from a large commercial project) obtain. Except as noted below, since then, I've detect no material degradation in cable testing, and, needless to say, it handled the leaps from 10 Mbit/s (1997) to 100 Mbit/s (2002) to 1 Gbit/s (2009) with no difficulties.
According to a new (borrowed) cable tester, all the runs look capable of sustained 10 Gbit/s.
At current rate of progress in speed that should take me at least to 2021 before I start noticing that I'm no longer keeping up.
Of course with my luck, in my area, broadband will still probably be 10 Mbit/s and capped at 90 GB/month.
In my (admittedly limited) observations, you can have about four sources for run destruction:
1. Work hardening and breaking due to excessively sharp bending. (Be careful on insulation, and teflon coating = nice -- makes cable much harder to bend sharply)
2. Oxidation problems especially at the terminal. I've had terminal problems with wiring in an indoor pool area (vapour barrier separating it from rest of the home). Salt water + generated chlorine seem not to like metal in general. People unlucky enough to have installed the Chinese contaminated drywall might have similar problems.
3. Tension on cable (especially at terminal). Buildings shift, flex, settle, and twist. And not just in earthquakes. Competent installation helps here, especially if you have to redo a corroded terminal and need more run length.
4. Renovation. Whether it's a nail through the wall, a drill in the wrong place, mistakes can happen.
5. Animals. Squirrels getting into the attic managing to destroy infrastructure in a friend's house.
I've not had problems with (1), (3), (4), (5) but friends have. I would assume (5) is not a big danger in most office environments, but one never knows. As I say, my experience is primarily limited to my home and those of friends who've also wired up. And my sole problems have been at the termination point, not with cabling itself.
My advice is... buy good quality cabling -- better quality than you need. Don't get your installs done by cowboys, and try to think ahead.
Tough advice sometimes to follow when you don't control the budget.
-Holmwood
Re:Overkill... (Score:5, Informative)
While you can link at those speeds with Cat5 you cannot actually get those speeds. Usually it tops out about 200-400mbit for me when I've tried. For most uses that's perfectly fine but in some cases it's not like my entire graphics and video editing departments. Servers are all connected with Cat6 if they use a lot of bandwidth.
I ran into this problem in Vegas as the place only had Cat5 connecting all the rooms to their closets so I had to use LACP trunking to get my bandwidth up.
Spend your money on a cable tester not wiring. (Score:2, Informative)
A good cable tester (say, a Fluke for example) is extremely expensive, but not as expensive as the man-hours involved in re-wiring an enterprise network because "maybe I think it might be worn out".
Seriously, get a good tester, and it will tell you exactly which wires you need to replace. People on slashdot are just guessing, they have no freaking idea if your wires are any good (apparently you don't know either, but a tester will fix that problem for you).
Re:Overkill... (Score:4, Informative)
Are you sure it's not your NICS/Servers/Switches? I remember seeing 250-400Mbit over Gigabit Ethernet a few years ago on older machines. Newer stuff particularly servers seems to be able to get close to a full Gigabit over the same cabling.
I suspect the bottleneck is actually the ability to deliver data and not the cabling.
Jason.
Re:So I got a new sink..... (Score:3, Informative)
Should I have a plumber re-run copper all over my house?
If they soldered those pipes with lead... Then yeah.
But that had nothing to do with your sink.
Er... not really. Although there may be a small risk for potable water, most of the pipework inside a house is for non-potable water. Taking the lead out of ALL solder (RoHS) is about protecting plumbers, not householders. If you have existing Heating and DHW systems jointed with lead solder, leave them be - they will be far less prone to leaks than any of the current lead-free solder compounds.
Re:Overkill... (Score:5, Informative)
5 and 5e are only rated for 100MHz per pair, so although you can get link speed aggregated at 1000bT, your max throughput due to crosstalk, signal reflection, and EMI is going to limit your switch to a speed closer to 300-400Mbit. Many switches will detect Cat-5 issues and downgrade your link connection automatically on problematic runs.
Connector quality has more to do with the connection quality than the cable itself. 5e simply has tighter specs to maintain. Really, there's not much of a difference, especially is you're using good patch panels.
Cat 6 runs 250MHz per pair, tru gigabit speeds are supported.
10G over copper is most commonly limited to 15M, and requires special 4 lane copper cabling, not Cat6 cabling. It's similar to Infiniband in design. A Cat 6 option was later offered, though few companies support this format. It's limited to 66m, and suffers similar bandwidth issues due to signal quality that running Gig-e over Cat-5 exhibits. Cat6a cabling can be used for 100m 10G deployments. Note this requires 650MHz Cat 6 cable ends, not 250MHz cat 6 cable ends as are normally deployed, for which there is a difference, and also requires 10G rated patch panels. Cat 6 cable can come in one of 3 thicknesses (guage). only one of these is commonly reccomended for 10G speeds.
Cables do go bad over time, due either to environmental factors or movement. Exposure to direct sunlight is bad fort cabling. Non-constant temperatures is also a cause of degredation.(cables in plenem space or inside walls tend not to remain at constant temperatures). Oxidation of the copper connector is the most common failure. higher quality cables and patch panels use silver, gold, or other corrosion resistant metals for this reason. Many cables are also made with lower quality plastics that simply fail over time (some are practically designed that way I sometimes feel). When the plastic fails, the cables corrode quickly.
More often I find a switch port fails before a cable (usually because someone plugged something in they should not have, or a charge makes it way into the cable due to being too close to a power cord, or long term exposue to magnetic fields causes elecrical resistance and damages the switch over time.
typically, I'd leave cables in place until a hardware upgrade or data bottleneck justifies the change. ALLWAYS use high quality cables rated for the installation location. lower guage (thicker copper) are generally better, but they should ALLWAYS be within spec. Buy cables from companies that offer 20 year lifetime warranty. (Hitachi, Mowhawk, etc) Have them installed by professionals who back that warranty and use properly rated panels and punch downs and you should have no issues. Anytime you;re running cables, allways run a class of cable 2-3 tiers better than your current needs, and for workstation drops or other complicated runs, allways run spares (the labor typically costs more than the cable, and running 2 or 3 at once costs less than 1 now and 1 later). Use cable trays or hooks EVERYWHERE, never let cables lie on ceiling tiles or underneath floors in channles.
This sounds like overkill, and probaly is for a small business, but when you have 14,000 desks in your copmpany (most with 2 netowrk and 2 phone drops) and over 3,500 servers, labor to replace cabling tallies in the millions of dollars...
Re:Overkill... (Score:5, Informative)
Although shielding is nice to have, it's not necessary for network cable because network cable is balanced twisted pair. Indeed, most high-performance network cables are not available with shielding, they can't maintain the spec with a shield in the jacket. It might be that your cable is older.
If you do have shielded cable, don't ground both ends!!! Bring all cables at one end to a common ground, and let the other end float. Otherwise, you will create a ground loop and actually make the noise worse.
Re:Gold plated baby! (Score:1, Informative)
Seriously though, what strange question. Either the cable works and you're happy with the bandwidth it provides, or it stops working and you replace it, or you want to upgrade it. What's the complication here?
Well, you do sometimes get iffy cables & connectors. They get yanked on all the time.
But the best thing is to get a real cable tester and measure for yourself. An actual cat5/5e/6 tester can be expensive, so you might just rent one or hire someone to test your cables for you.
Re:Gold plated baby! (Score:3, Informative)
This is absolutely nonsense. 1Gbps Ethernet is 1Gbps Ethernet. The signaling from the Ethernet controllers on both sides will be identical no matter what kind of cabling you are using. The only thing that will affect practical transmission speeds is if you are getting transmission errors in the Ethernet frames and they have to be resent. Heck, you could probably get a solid 1000BASE-T connection on coat hangers if they were short enough.
Re:So I got a new sink..... (Score:5, Informative)
Well, oddly enough I did IT work for a plumbing company. One of the things they did was "repipes" of residences. Usually they were done due to recurrence of leaks. Copper pipe corrodes from the inside because of chemicals in the water (like chlorine). Sometimes it was done where there was minimal water flow, when corrosion or sediment didn't wash away, but built up.
So, if you got a new sink because you were changing the rusty faucets and then you found your water flow wasn't improved, you may be a candidate for repiping part or all of your home. It could just be buildup in the shutoff valve too.
But to stay on topic......
I've seen people run network cables over or under their carpet. They start getting degraded service as people walk on it. Yes, those need to be changed. Properly run network cables (in the walls, with no rat infestations to eat the cables) don't generally need to be changed, unless something else happened. And I have seen network cards that handle regular CAT5 at speeds over 100Mb/s with 1000baseTX interfaces. Sometimes you can just reterminate the cables because the "spare" 2 pairs were never wired right, assuming those extra wires are ok (i.e., the installer didn't yank the cable through and bugger it up.
But, realize (to the OP) that there are limitations to GigE on a computer. Most of the time in the real world, you won't see 1000Mb/s. It's dependent on the switching hardware, PCI/PCIe bus, hard drives being read from/to, etc, etc, etc....
Re:Overkill... (Score:5, Informative)
Grounding one end makes the shielding at the ungrounded end an efficient antenna, and can actually increase the radiation from the cables.
Cable shielding isn't a good way to avoid inteference with the signal on the cable, and isn't a good way to avoid radiation by the signal on the cable, unless properly terminated for one specific frequency (or narrow frequency range). One or both ends of the shielding would need to be coupled to case ground by a capacitor chosen for the frequency that you want to shield.
Shielded cable at this frequency is likely to cause more harm than good. There's usually little need to shield against common-mode interference, and I've never heard of shielded cable being used in a TEMPEST set-up (carefully matching impedances is the best way to avoid emissions, creating giant gorund loop antennas is not).
Re:Overkill... (Score:4, Informative)
So, yeah, how did that shielded unshielded twisted pair work out for ya?
Re:Overkill... (Score:1, Informative)
A simple ground loop which acts as an antenna doesn't hurt the signal too much. The real problem with grounding both ends of the shield only occurs when the two ends are connected to different ground potentials, e.g. in different buildings or in different parts of one building without common ground: Then a strong current will flow through the shield. This is a fire hazard, because it's basically a short. Additionally the strong current can damage equipment connected to the cable. Electric wires with shielding should never be used between locations with different ground potentials, unless care is taken that the voltage between two ground connections doesn't exceed a safe threshold.
Re:Overkill... (Score:5, Informative)
He said FTP, which is also known as S/UTP, screened unshielded twisted pair, or "fully shielded" twisted pair.
The difference between FTP and STP is that in STP, each cable pair is shielded.
FTP has only an overall shield that covers all the pairs (each pair isn't individually shielded).
So FTP _is_ shielded UTP.
Re:Overkill... (Score:3, Informative)
Read and learn:
http://en.wikipedia.org/wiki/Foiled_twisted_pair#Cable_shielding [wikipedia.org]
and http://lmgtfy.com/?q=ftp+cable [lmgtfy.com]
The FTP cable has a steel wire in the center, each pair is shielded and then all pairs are again wrapped in aluminum foil.
Yeah, shielded unshielded sounds bad, but for most people it's the easiest to understand the difference.
Re:So I got a new sink..... (Score:3, Informative)
The trouble with ethernet is it's negotiation scheme only takes account of the capability of the end devices, NOT the conditions on the line in between them (this is different from something like modern ADSL which negotiates a rate based on line conditions).
So if your cable is not up to gigabit (cat5 should theoretically support gigabit but only if it's installed absoloutely to spec and the run isn't too long), you put gigabit hardware at both ends and you don't manually (which opens it's own can of worms e.g. duplex mismatch issues) force the speed down it will try to run at gigabit and end up with a horrible error rate.
To put it another way for small networks with unmanaged switches make sure you stick to 100 megabit switches unless you are sure your wiring is good for gigabit.
Oh and make damn sure you don't have any "split pairs" (two lines that should be on the same pair on different pairs), those will cause horrible error rate even at 100 megabit.
Re:Overkill... (Score:5, Informative)
5 and 5e are only rated for 100MHz per pair, so although you can get link speed aggregated at 1000bT, your max throughput due to crosstalk, signal reflection, and EMI is going to limit your switch to a speed closer to 300-400Mbit. [...] Cat 6 runs 250MHz per pair, tru gigabit speeds are supported.
That is incorrect. Gigabit Ethernet (1000BASE-T) uses the same bandwidth as Fast Ethernet. The higher speed is achieved by using
1) all four pairs (Fast Ethernet uses two),
2) each pair in both directions (Fast Ethernet uses one pair to send, one to receive), and
3) a more efficient encoding (more bits per baud).
The full Gigabit Ethernet speed is specified for Cat5 cables.
Re:Overkill... (Score:3, Informative)
Re:So I got a new sink..... (Score:2, Informative)
With the exception of toilet water, all domestic running water is expected to be drinkable.
I don't know about the US, but in the UK this is certainly not true. Only mains cold water is classed as potable. Domestic hot water should never be used for drinking or food preparation, not because of the low risk from lead poisoning, but the very real biological risk it presents. Recent regulations here regarding sealed and screened header tanks (also increased use of combi boilers) do something to ameliorate this risk, but seriously, if you are ingesting domestic hot water then lead poisoning is the least of your worries, especially if you follow recent guidelines and set your DHW temperature to a bacteria-friendly 38-40C instead of the old-fashioned 60C. (Apparently it is very dangerous for hot water to actually be hot).
I don't think dish-washing or mixer taps present any real danger (metallic or biological), as the amounts ingested are verging on the homeopathic. Even taking DHW into account, most domestic pipework is taken up by the heating circuit. Unless you drink the little squirt of water that comes out when you bleed the radiators, you are better off sticking with existing lead-solder joints here.
Compression fittings would be a better choice for a new installation, because current lead-free solders are really not fit for purpose. Plastic push-fit systems are also a possibility, but I would prefer to wait 5-10 years to make sure the current generation really don't suffer from the seal degradation problems of earlier systems - (then again, is plastic safe?).
Finally, most UK toilets are plumbed directly into the mains, so as long as you drink from the cistern rather than the pan, it is a lot safer than the hot tap.
Re:Copper vs New Materials (Score:3, Informative)
Yep, and that's what our best scientists are working on. In the meantime, though, we shouldn't get too scared about resource scarcity. All I mean is that we're not going to have to shut down the LCD factory in 4 years.
See, for example, the progression of aircraft structural materials: wood and canvas, aluminum, aluminum alloys, magnesium, fiberglass and aramids, titanium, carbon fiber, and now I hear that maybe someday they will be constructed with special ceramics. (I left out the soviet union's brief foray into steel aircraft since that's been around for a while)
Titanium is a good example of relative scarcity vs demand; it is one of the most common materials in the earth's crust, yet only recently has it been economical to produce in bulk. This was driven by military needs, and I wouldn't be surprised to see the newest breed of materials also come from military labs.
-b
Re:Overkill... (Score:4, Informative)
Sure, it's a little like an antenna, insofar as a Faraday cage is.
But grounding the shield at both ends creates ground loops. You might not notice them right away, but you sure will the first time the MOVs in the surge suppressors at one end or the other shunt a spike to ground, and some of that current decides that its preferred path to ground is over your STP Cat5.
Eventually, after you blow up enough switch ports, you'll stop doing it that way.
It's generally pretty bad form to ground both ends of any shielded wire that traverses any real length.
Re:Overkill... (Score:3, Informative)
Whoever did your cabling was unqualified to do the work he was hired to do. (Usually the the fault of whoever hired them.)
I don't follow... When I get a quote from somebody who claims to be capably trained for certain task how is it my fault when he screws up?
I don't think that's what he meant. If you call Company A to do the work, and the guy Company A sent is incompetent, it's the fault of whoever is in charge of hiring people over at Company A. It doesn't mean that everyone in the same class as Company A are incompetent for that job (ie, all electricians). Sometimes, it doesn't even mean everyone at Company A is incompetent.
More things to look out for.... (Score:5, Informative)
Not only can your gear affect your speeds, but conflicts with speed auto-sensing can wreak havoc.
We recently swapped out some older edge switches in one site for a beautiful new CISCO core switch. Within days, the help desk had reports that some users' network performance had gone from fine to terrible. (Not our intent.)
As it turns out, a boatload of older NICs were mishandled by the new switch which downgraded speeds, communicated in half-duplex, and even then continually reset the connection.
Had the users not complained, we never would have known there was a problem.
As it turns out, each port on the core switch can be manually set to a fixed 100mb full duplex (and ignore auto-sensing) which then operates just fine.
So much for plug-n-pray.
Re:Overkill... (Score:5, Informative)
You talk about grounding like folks used to talk about SCSI termination[1].
The reality is far simpler, and there's no goat's blood required: Use shielded wire where it makes a difference. Ground it at one end (or in the middle if that's what the situation dictates, but under no circumstances at more than one point).
And then, have a beer. While imbibing, rejoice in the fact that one's cell phone has ceased ringing with voices proclaiming connection issues.
[1]: SCSI buses should be terminated exactly twice; once at each end of the bus. If you have more than two terminators, they are in the middle of the bus, or your "bus" has more than two ends, you've done it all wrong and need to start over. Same with TV coax, radio coax, 10base2, or any other transmission line medium.
Re:Overkill... (Score:4, Informative)
Bullshit - you just hired stupid electricians. Probably lowest bid on the job, right?
We let our contracted electricians run our coax, cat5e, 110v, 208v, and 480v - and they did a great job. Even labeled all the ports on the patch panels, each end of the cables, and even used the cable management we installed.
Data wiring companies are just over priced electricians.
Replacing Cable - It Depends (Score:1, Informative)
Long time SlashDot reader, first time poster... That being said, I think I can add to this topic.
I'll start off by saying that I'm a "sales guy" for a cable manufacturer, but I'm still an engineering major at heart, so I'll remain very objective (and also short and sweet) in my conclusions here. I'll assume an all-data network.
Network cables should be replaced, but sometimes, it doesn't make sense. It mostly depends on what your starting point is and what your "migration strategy" is.
You can have a good, long discussion about the benefits of better cable, but here's a quick synopsis.
-Cable can be both a very simple and a very complex thing--it depends how deep you want to get into it. I won't get very far into it right now.
-There is a lot of offshore cable that is made and labeled as cat 6 or 5e, but aren't actually cat 6 or 5e. This should generally be replaced immediately.
-Category cables don't get "old" on their own (usually new standards make cables obsolete before anything else), except in cases of cable abuse, which are common--if not treated properly for what the cable is designed for, the jacket could wear out, the pairs could get separated, water or other environmental factors could harm the cable, etc. The end result is always the same--they will start to show worse electricals and start to fail key tests (ACR, NEXT, FEXT, RL, etc.) that make them "cat 6" and "cat 5e" or whatever.
-When a cable wears out, they may still pass a simple connection test, and you'll still be able to connect to the network--but your computer will be busy re-sending the data, which will slow down the effective speed of the connection. That is, you may still be connected at 1 gigabit, but your connection may be getting throughput closer to 1 megabit. So, really, in the end the more headroom the cable design has the more throughput you'll theoretically get. (Headroom is the amount the cable exceeds standard.)
-Typically, the first thing that needs replacement in an Ethernet channel (i.e. - all the cable and connectivity from the computer to the server in a structured cabling system) are the patch cords, due mostly to abuse by the users.
-There's a lot of snake oil as to what good cables consist of. In thinking about the kind of ethernet cable to buy, these are all generally good qualities to have in a cable, some are more important than others, depending on the application. (I'll oversimplify a bit, but this should give the jist):
1- Pairs that are twisted tightly and yet vary between each pair within the cable. This reduces crosstalk and helps the frequency performance of the cable.
2- Pairs that are able to maintain the twist and not get untwisted with abuse. (DC Coupling between the pairs is important to how a UTP cable performs)
3- Shielding isn't necessarily a good thing--a poorly shielded cable system can cause more problems than they prevent.
4- A sophisticated separation device between the cables is always a good thing.
5- A cable that will randomize or vary pair position between cable to cable is a bonus, especially in the category 6a world--this reduces alien crosstalk, which is vital for future applications.
6- A floating shield can be nice to have, especially in a patch cord, depending on the application. (not a GROUNDED shield--note the important difference.)
7- A Low delay skew is preferable, though becomes more vital in other non-data applications.
8- If you only had the chance to look at one electrical parameter, ACR is a good place to start--the frequency that the ACR crosses 0 for the entire channel is a good ethernet system.
Denon AKDL1 Dedicated Link Cable (Score:4, Informative)
I'm sure you meant to use this link for the best price - the comments here will fill you in on the AWESOMENESS of these cables.
Denon AKDL1 Dedicated Link Cable:
http://www.amazon.com/Denon-AKDL1-Dedicated-Link-Cable/dp/B000I1X6PM/ [amazon.com]
Re:Overkill... (Score:3, Informative)
There are generally two schools of thought on grounding:
The problem with choice 1 is that the length of the return path can become long enough to become significant when compared to the frequency of the signals of interest. When this happens, your ground isn't really ground anymore.
If you want proof of this try probing a 1 GHz signal on an o-scope using a 6" ground lead, instead of the very short ground pin provided with the probe. (You'll need a multi-GHz o-scope and high frequency probe for this experiment obviously.)
A "tree" style grounding is more practical for low frequency signals, or special situations.
If you want to learn more about all of this, I recommend MIL-HDBK-217. [tscm.com]
See sections 5.4.1 and 5.4.2 to start.
Re:More things to look out for.... (Score:3, Informative)
Re:No (Score:2, Informative)
Re:So I got a new sink..... (Score:3, Informative)
I am not a professional plumber but I have done a fair bit... As I understand it your hot water should be stored at between 60 and 70 deg C to prevent legionaries, any hotter will cause scale build up. The 38 to 40 deg C is only a requirement in places where the general public may be using the hot water (all council buildings have hot water that is tepid). The main store of water is still held at 60 to 70 deg C it is simply blended near the point of use down to 38 to 40 deg C.
As for plastic pipes I would choose them over copper any day for the simplicity of fitting. I've never had a joint go bad after fitting miles of the stuff. I do, however, always make sure I use polythene based pipes and not the poly-butyl based ones. The butyl pipes are softer but there are some questions over them leaking plasticisers into the water.
Re:So I got a new sink..... (Score:3, Informative)
Dear god man.. its not really that degraded of living outside of the USA is it??
Yes, it is... I was amazed when I moved to the UK & first saw how the water supply worked. To an American, the thought that you could have a (dead) pigeon in your water tank is horrifying; in the UK it's just accepted. See about 4 minutes into this classic Fawlty Towers, for example:
http://www.youtube.com/watch?v=UJ-sRQ1oTxc [youtube.com]
Half of the places I lived didn't even have the most rudimentary of covers over the tank; the worst was a large open lead lined trough. A lot of my British roommates didn't even realize that drinking from any tap other than the kitchen cold tap was a bad idea, despite most of them having tales of bad stuff happening in their houses. The best one was the bathroom tap which stopped working; the plumber found their missing hamster clogging the pipe...