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I recently read a person put a 300' roll of Pex coiled tubing in his attic as a Collector and heated (preheated) his water that way. My house attic in Florida has to reach 130 f in the summer and at least 90 f. in the cooler months. Anyone consider doing this ? Pros /cons ??? Thanks.
Any disadvantage to going up one layer to the rooftop?
That would take the heat Before it got to the attic.
But overall, you are correct, it would heat the water being circulated as you describe -- and take some (very limited) of the heat out of the attic.
Have a friend who does designs where water is circulated around attic vents. While the hot air is blown out through fins, water tubing is heated and directed down for water, pool heat, etc.
An old house where my mother and step father lived in many years ago (in northern CA) had copper pipes run in the attic space to get to a bathroom in the back of the old house. The original old pipes in the concrete slab had failed, and the only easy way to get new pipes across to the back of the house was through the attic. In summer the water in those pipes would get so hot that it was difficult to get cool water out of the faucet to reduce the temperature of the "hot water" from the water heater. So there is little doubt that a hot attic contains enough heat to work as a water "pre-heater" in a warm climate zone.
I think your idea is great, and it seems like it would not be expensive. In FL it would make even more sense than putting some kind of solar direct water heating system on the roof. In FL hurricane season, the last thing you would want is a bunch of expensive, heavy stuff on your roof getting blown off, and then leaving you with water pipes broken and leaking through the holes left in the roof afterwards. The PEX in the attic would be safe from heavy winds outside assuming the roof and house remains in place.
If I was going to do this I'd research how well it would work using a thermosiphon so you could heat a great volume of water. 300 foot of 3/4 pex is going to heat maybe 10 gallons at the most.
The basics are you would have the cold water inlet come into a looped system. The first component would be a way to transfer a lot of heat to a small amount of water such as having pipes painted black on the roof. This pipe would have one end connected to the top of the storage tank and another end connected to the bottom of storage tank. The heating pipe should probably slope upwards gradually. The storage tank has to be above the pipes heating the water. As the water heats up in the pipe it will naturally circulate into the top of the storage tank with the colder water circulating back into the pipe. You would probably want to insulate the tank and some of the pipe near the top to prevent heat loss during the night.
You would also have outlet somewhere in the loop to feed the hot water tank with a check valve especially if it's below the storage tank. This will prevent hot water from circulating out of the tank.
It's a slow process but quite effective when used with a solid fuel heating sources and in that case the storage tank is usually the hot water heater itself. The only issue with the solar is might be too slow a process.
Last edited by thecoalman; 07-13-2011 at 04:05 AM..
I like the idea of attic heat warming up the water in the Pex coil as i take my daily shower at 6 pm each day, and dont require alot of hot water since i live alone...a 95 f. shower suits me fine or even 90 f. I would simply splice it into the hot water supply line right off the water heater, then route it thru the attic Pex tubing and back into the house hot water supply line. Cant get any simplier than that ... and i can locate the attic Pex coil directly above the water heater to minimize the run. That eliminates messing around on the roof, building a collector box, no pump, no controls, no UV light which destroys plastic tubing, etc... 5-6 gallons of warm/hot water is all i use each time...and thats just for a quick shower .
I would simply splice it into the hot water supply line right off the water heater, then route it thru the attic Pex tubing and back into the house hot water supply line.
If it's after the hot water heater you're not gaining anything because you'll still have the same volume of cold water going back into the tank. Actually you would going backwards because the you'd being leaving a lot of hot water in the pipes.
Whether you try what I suggested or just use the pipe by itself the best thing to do is have it run into the hot water heater as the feed. Every time you wash your hands, take a quick shower, run the dishwasher or run the clothes washer you're replenishing the hot water heater with hot/warm water. It has to work less to bring it back up to temp, if you can live with warm water just turn the temperature on the tank down.
If it's after the hot water heater you're not gaining anything because you'll still have the same volume of cold water going back into the tank. Actually you would going backwards because the you'd being leaving a lot of hot water in the pipes.
Whether you try what I suggested or just use the pipe by itself the best thing to do is have it run into the hot water heater as the feed. Every time you wash your hands, take a quick shower, run the dishwasher or run the clothes washer you're replenishing the hot water heater with hot/warm water. It has to work less to bring it back up to temp, if you can live with warm water just turn the temperature on the tank down.
Ill have a full 6-7 gallons of hot water in the Pex tubing that will be going into the house hot water supply line to the shower i take, and if that temp. is at say..130 f from the Pex Collector then ill have to cut the flow of the hot water using the faucet and open the cold water ; so I may not even have to use the 6-7 gallons of water from the Pex. Plus, i dont use hot water for clothes washing and i use the auto dishwasher once every two weeks. My hot water useage is quite minimal which is why i dont think i need a 30 or 40 gallon storage tank --- I would never use that amount at one time.
This seems like a good idea to me and inexpensive to implement, so why not try it? The only downside that I can think of, is if you had a power outage in the winter and the inside temperature of the attic fell below freezing. You wouldn't want water leaking over your ceiling. An attic well insulated with spray foam insulation to cut down on drafty corners might help. It's worth a try I think.
Ill have a full 6-7 gallons of hot water in the Pex tubing that will be going into the house hot water supply line to the shower i take,
Still wont work well or at all. Water is going to follow the path of least resistance and if that means going through the hot water tank that's where the supply will flow from. For example if you had faucet with Y and have 10 feet of pipe on one end and 300 feet on the other very little water if any is going to move through the 300 foot section.
Still wont work well or at all. Water is going to follow the path of least resistance and if that means going through the hot water tank that's where the supply will flow from. For example if you had faucet with Y and have 10 feet of pipe on one end and 300 feet on the other very little water if any is going to move through the 300 foot section.
Im afraid you misunderstand ; I wouldnt be sending the attic heated water from the Pex tubing back into the water heater at all....it would be going into the hot water supply pipe that i had cut directly above the water heater. Heres how the water would flow : Opening a hot water faucet in the house would allow the line pressure to force water out of the water heater into the supply pipe right above it then immediately divert up to the attic and thru the Pex tubing where it would circulate thru the Pex tubing then flow down to the hot water supply pipe that i had cut which leads to all the house hot water faucets. Can u envision this ? No attic water is ever returning to the water heater...only thru the hot water piping to the house.
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