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Question DetailsAsked on 2/6/2016

Water is hot at the heater, but cold at the faucet. Is the cause likely to be heat loss from uninsulated pipes?

I'm in south Louisiana, where the current air temperature is about 40 Farenheit and the average ground temperatures is around 65 Farenheit. Houses here typically have the water heater attached to the back side of the house, and the pipes are usually uninsulated and run under the floor joists in an open crawl space.

But on the house we're currently rehabbing, the water heater is in a shed about 15 feet behind the house, with the pipes run underground. My partner thinks that the water is hot at the heater but cold at the faucets due to heat loss from running the pipes underground, and that we should move the water heater closer to the house. I think that the ground is sufficiently warm and the run sufficiently short that that is not likely to be the cause of the problem, but I don't know what else it could be. The water has good pressure from both hot and cold taps at all faucets in the house, but it's cold from both taps.

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1 Answer


OK - if you let the hot water run a few minutes and is still COLD - same as from the cold faucet - then you are not plumbed into the hot water heater or it is not on or working right. Check the temperature at the outlet pipe from the water heater (don't burn hand) but should be too hot to comfortably hold onto when you run the water - typically 120-130 degrees. Then feel the pipe where it comes into the house - should warm up nicely after a minute or two of flow, though likely to be down to only about 70-100 degrees after 15 feet of in-ground run. If does not warm up at all then the water heater is not plumbed to the faucets for some reason, or is not working at all (or turned down to low setting).

Certainly, if the water comes out and warms up from house temp to lukewarm or better at the faucets then the cold ground is doing it. Note you said 40 degree air temp - in your area, that pipe might be only about a foot or less down (especially if a DIY job) so the ground temp around the pipe might be more like 45-55 even if 65 at depth - a 15 foot run in close contact with that temperature soil makes for a heck of a cooling system on the pipe. Especially if saturated, so you are heating up not just soil but also groundwater.

Moving the water heater up against the house in a utility closet (or inside) makes sense to me because you eliminate all the cooling effect, especially as with the unusual weather occurring these days that would likely get the cold water feed out of the shed too (so minimize risk of freezing, unless this is a pump shed).

Other alternative, which is possibly but not necessarily cheaper, would be to dig up the pipe and replace it with an preinsulated in-ground pipe (though would be special order from your area) - the pipe is a double wall pipe with foam insulation between the two pipes. Do NOT use the fiberglass insulated type - that is only for above-ground use - useless if it gets wet as it would underground. Runs about $5-7/LF for the in-ground type (also comes in in-house type for runs to hydronic heating systems). You could also build a utilidor out of Dow HI-40 or similar closed-cell insuylation board around the pipe - I have not run the numbers, but probably about 4-6 inches would do it in dry ground - in wet ground would have to be sealed in watertight to avoid heating the groundwater with your hot water feed. However, even if insulated, the initial water coming out of the pipe will be at ground temperature - so a lot more customer friendly to move the heater to the house close to the bathrooms to eliminate that waste and discomfort.

Answered 4 years ago by LCD

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