Coil of Black PVC to Preheat water?

[Waxman]

At the plumbing supply today, I heard an interesting idea:

Running a coil of black PVC 'Well" line in a sunny location to preheat pool water.

Why not use this idea to preheat carwash water?

Is this an easy and simple and low cost way we could preheat (or completely heat in Summer) our wash water or am I missing something that makes this idea a 'no-go'?

 

[ted mcmeekin]

This will work although you need run some numbers on how much water you are trying to heat to what temp. My gut says you probably can take a hot shower but it will probably take a mile of ABS line to make an appreciable difference in water heating bill. Figure out how many btu's you are now using to heat your water and then calc how much line to make a difference--need make some assumptions. Don't forget that you are adding pressure drop your water source.

Ted

 

[MEP001]

It's an interesting idea. I have a 500' spool of 3/8" black poly tubing whick I can string out across the roof and run some water through. I'll have to remember to try it when it warms up a little.

It might be more effective to use a circulator pump with a reservoir of some sort, or cycle water through a length of the plumbing that feeds the boiler. For greatest savings, it would need a solar-powered pump.

There was a local wash with a large array of solar water heating panels on the roof, but they were allowed to freeze and were ruined.

 

[MEP001]

Looks like they're still there:

 

[PaulLovesJamie]

Solar water heaters for domestic hot water produce approx 35,000 btus per day of sunshine. Coiled-up black pvc is basically a cheaper system ... and significantly less efficient. Is it better than nothing? Yeah, probably. But not worth the effort IMO. I'd be interested in seeing numbers if you forecast a reasonable payback.

 

[Whale of a Wash]

Last summer during a redo of water line and street at our wash I got hooked to a fire hydrant about 600' away, but with 3'' pvc in white. I felt it gave about a 20 degree rise, and for two weeks turned the palomas almost all the way off. It made quite a difference. I thought if i had coiled that much tubing on the roof or put a black 1000 gal tank next to the building the gas bills would go down alot.

 

[Waxman]

Hey, that's another super idea; a big, black plastic tank outdoors that the washwater circulates through. Coupled with the black pvc idea this could be a real winner, I think. I bet I could cover my roof and install a black tank and recirc pum for a couple grand.

Man, we're coming up with some great ideas here!

 

[pitzerwm]

Remember to "shield" the black tank and probably the hose with a clear plastic (mylar will last a lot longer) to cancel the loss due to the "wind" passing over them. I once paid a solar expert for an hour of his time. He showed me a very cheap and simple "panel" that anyone could build and it was very efficient. You build a shallow box with the inlet at the bottom and the outlet at the top. The thickness of the box was 1/2", the "depth" of the water was 1/4" then you had a layer of Mylar with another 1/4" gap and another layer of Mylar. The water was circulated with a small pump as you can see the temp will rise each time the water circulates. Someone smarter than I could figure out how big the tank needs to be and how many panels you would need to make a difference, but you can see that it is a cheap way to do it. The smaller the diameter of the tubing in your black hose approach would be more efficient or circulate the water slower for max heat transfer. It would be easy to determine efficientcy by putting a tempature gage at the inlet and the outlet.

 

[Waxman]

Mentioned this idea to my equip. dist. His propane is $2.30/gallon and this would benefit him alot.

 

[easywash]

Great idea

here is an example

http://ca.youtube.com/watch?v=sBAi_TVNaiM&feature=PlayList&p=12CC5BC5D5919569&index=0&playnext=1