Water heat transfer

[slabghost]

Okay so the cold season has begun here once again. Incoming water supply gets cold enough to quickly cool the hot water tank. All summer the capacity is plenty for a shower but now it's getting to where I need to be fast or get chilled. I know a larger tank would compensate but it will still be chilled from the incoming water more than it was during the summer months.
So this gives me an idea. What if I extend the line through a lot of back and forth piping before it enters the tank? Should work like a reverse radiator absorbing the heat from the warmer basement air before it enters the water heater.
Now the big question. How many feet of 1/2" pvc pipe will it take for the water to gain say 30 degrees from ambient air? Any guesses?
:thanks:

 

[dan filipi]

You could in reality create a storage tank of ambient temp water by using enough pvc. How much I don't know but I'd start with a couple hundred feet. Stuff is cheap and more is better.

 

[dan filipi]

Something about water heaters too is they have a 'dip' tube that can break. Purpose behind them is to route the incoming cold water to the tank bottom below the hot water. If it's leaking then hot water can be greatly reduced.
This was happening on ours. A new one made a huge difference.

 

[mcgovern61]

Slab, do you have an electric, oil or gas water heater? If electric, it is very common for an element to burn out and have only one making hot water.

 

[ekvh]

An uncle of mine just set up a second tank near his wood stove. It worked well and reduced electrical bill. He wanted it up in the floor joists but opted for a few cement blocks. In some climates you may have condensation issues to deal with. (Insulate it)

 

[slabghost]

mcgovern61 » Mon Nov 21, 2016 6:35 pm[/url]":1v1ueqj3]
Slab, do you have an electric, oil or gas water heater? If electric, it is very common for an element to burn out and have only one making hot water.

It's electric but nearly new. Still worth checking the heater element. After Dan's suggestion I'll be checking the dip tube too.

 

[slabghost]

ekvh » Mon Nov 21, 2016 6:35 pm[/url]":nmomqiww]
An uncle of mine just set up a second tank near his wood stove. It worked well and reduced electrical bill. He wanted it up in the floor joists but opted for a few cement blocks. In some climates you may have condensation issues to deal with. (Insulate it)

I considered the extra tank idea but I expect the water would take quite a while to warm to room temperature. Which is why I'm considering a sort of reverse radiator.

 

[backlander]

Any thoughts in the direction of a solar water heater? Pretty simple to make, could use it as a preheater or main heater with the electric as a back up.

 

[Tom_Charlton]

The idea has merit, but there are some drawbacks.

1. PVC doesn't conduct heat very well. If you can afford it, copper or aluminum will do a much better job. Best would be the A-coil from an old air-conditioning system.

2. Locate the heat exchanger (yes, that's what you're talking about) in a heating duct, next to your furnace, or a room that gets a lot of sunlight.

3. Use a box fan to force room air past your apparatus. You will get condensation as the room temperature air is cooled by the incoming water, so put a drain pan under the apparatus.

4. "TANSTAAFL : There ain't no such thing as a free lunch." (Robert Heinlein). The energy used to warm the water must be replaced by your heating system or something.

Solar pre-heater for water: Build a box 8' long, 2' wide, & X 1' deep. Paint the inside black and insulate the outside. Locate it on the south side of your house at ground level. Build your coils from 1/4" pipe (the smaller the pipe, the more surface area exposed to the water) and get as much feet as possible in the heater. Paint the coils black also and cap the box with glass (old double pane storm windows would work fine). Run RV antifreeze in the outside exchanger to prevent freeze-ups. Build the indoor heat exchanger next to your hot water heater. Make this one higher than the outside one and you won't need a pump due to the warmed antifreeze rising. Run your incoming cold water thru the inside heat exchanger out to your normal water heater. Let me know if it works!!

If you could capture the hot air & methane I created writing this, you wouldn't need a water heater.

 

[slabghost]

Well not looking for a free lunch....unless you're in the neighborhood and buying. Yes heat exchanger is the term I was missing. I don't really have the space for a solar water heater and they aren't exactly good looking. I could put one on the roof but that gets very pricey. I agree metal will transfer heat much better than pvc but it also corrodes over time. Just the wife and myself here. So need for the hot water should be infrequent enough to warm enough between uses. I'm thinking of forming the heat exchanger to resemble a roll of fencing and use just a tiny fan to keep air moving through the unit.

 

[Ansimp]

+1 on metal for heat transfer. :good:

 

[BikerJoe]

:heat: :doh: im thinking :heat: a coil of Pex like tubing like they use fer under floor heat back and forth betwix tha floor joist if its access. Kinda reverse engneering heat extraction ? :doh:

 

[backlander]

That Pex is some good stuff, a little expensive on the front end but well worth it.

 

[BikerJoe]

slabghost » November 21st, 2016, 3:36 pm[/url]":229ld90r]
Okay so the cold season has begun here once again. Incoming water supply gets cold enough to quickly cool the hot water tank. All summer the capacity is plenty for a shower but now it's getting to where I need to be fast or get chilled. I know a larger tank would compensate but it will still be chilled from the incoming water more than it was during the summer months.
So this gives me an idea. What if I extend the line through a lot of back and forth piping before it enters the tank? Should work like a reverse radiator absorbing the heat from the warmer basement air before it enters the water heater.
Now the big question. How many feet of 1/2" pvc pipe will it take for the water to gain say 30 degrees from ambient air? Any guesses?
:thanks:

https://www.supplyhouse.com/sh/control/R ... Calculator
https://www.supplyhouse.com/sh/control/R ... torOptions
https://www.supplyhouse.com/Calculators

Try one hundred feet roll at a time till you have enuff :hi:

 

[Dadster]

If you have forced hot air heat, run pex through some duct first to preheat.

 

[slabghost]

Excellent idea!