Even using Nicks figures there is a glaring assumption that way inflates the figures. Although you did point it out, I will do so again. Water in the intake pipe is -not- going to warm up to ambient in less than several hours. In my house with just the two of us, water in that pipe will only remain there until the pump kicks in again. Given normal useage that will occur at least once per hour, oftener when watering. In a house on city supply, there will be an exchange of water in that pipe any time a faucet is opened or toilet flushed, etc. That will occur several times/hour for zero savings.
Now you might ask yourself what's really going on here:
I think the OP is saying the incoming water is warming up to the dew point of the basement air. If condensation never occurs beyond the first few feet of pipe, even when water is flowing, the pipe is warming flowing water in real time, which is a much more important saving than the warming of small amounts of water between uses.
Do you -really- think that water coming in at 50 degrees (IINM that is about normal underground temp) at high velocity, at least that of an open fixture, is going to pick up much useable heat in 10 ft?
I suspect he is referring to non-flowing conditions. I kind of lost track here. Does he say that it is in a basement? In my case it is and the pipe is coated with condensate from the point it enters until it disappears into the ceiling joists. Temp in my basement is around
if you leave the pipe uninsulated you will avoid the killer mold in the insulation problem, which is what you probably heard about on tv news last year. a spray-on aerosol can foam insulation would ease your mold worries if you insist on insulation. check with your local building inspector for requirements and ideas.
Sure, based on the OP's description and the fact that condensation can dramatically increase the air-to-pipe thermal conductance by a factor of
100 or more... 2 gpm is 960 Btu/h-F, so warming it 1 F takes 960 Btu/h, ie
1 pint of condensation per hour, about 3 drops per second. I can imagine that, in continuous use, altho most usage bursts are a lot shorter.
It might make sense to change this pipe to fin-tube vs insulating it :-)
Yes, the condensation only appears on the first 6 feet or so of the
1" pipe. That pipe runs vertically near the basement wall where the city supply enters. The 1" pipe is pretty dry after it turns horizontal and continues to be dry as it branches off to the water heater and converts down and branches to 1/2" pipe runs for the house cold water supply.
About 1/3 up the initial vertical 1" pipe run, the 1" pipe bifurcates to supply the underground sprinkler system. This bifurcated pipe rises in parallel with the rest of house supply for about 3 ft and then exits the house. This run also "sweats" heavily.
My initial thought was that the 2 hour runs of the sprinkler may be primarily responsible for the sweating. However, I have not noticed significant variability in the condensation between days (and times) that the sprinkler runs vs. when it doesn't.
Also, the rest of house supply pipe continues to have heavy condensate for 2-3 feet above where the sprinkler branches.
Also, btw, we heat the hot water with gas and we live in New England.
Finally, last night I insulated the first 10 feet or so of the 1" runs (except around the valves and water meter), plus the branch to the sprinkler system.
We will see what happens (though today is significantly less humid so it may not give it a good test).
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