Bright idea for saving money on your water heating bill.

[Donald H]

Yes the copper would be better but it's so much more expensive and harder to work with. Using pex you can get an unlimited length and work with it rather easily simply using shark bite push to fit couplings. The whole job can be done in less than 2 hours. Running copper would require a lot of measuring and cutting but still I agree the copper would be better. And no I would not run the pex out in the sunlight. I have an enormous attic.with 45° pitch sides making the total surface area exposed to sunlight roughly 166% of the deck area. It is a massive heat machine. Running 100 ft of pex ln a coil through this environment makes for a rather efficient heating process prior to entry into the water heater. There's no pumps I'm moving parts just city water pressure doing the job.

You need to do some engineering calculations. What will the air temperature in the attic be, compared to the temperature rise available from the sun's radiant heat?
But what am I doing making suggestions as a lay person, to someone who has proclaimed to be an engineer?
Let this one go! The holes in the theory are wide enough to drive an 18 wheeler through.

Fwiw, your 6/12 pitch in the attic doesn't make a goddamn bit of difference. You're trying to rescue your original idea by inventing a hybrid!

 

[progressive hunter]

I'm pretty fortunate there I have a pipe chase with visual clearance from the cellar to the attic.. but yes I could see what that would be a problem in some places.

I think about before I insulated the roof on my metal shop building,, the temp gauge was reading about 145 degrees at the surface inside the building with an outside temp of 85 degrees,,

sometimes the problem could be it gets to hot and you need to run cold water to lower the temp,,

 

[justoffal]

You need to do some engineering calculations. What will the air temperature in the attic be, compared to the temperature rise available from the sun's radiant heat?
But what am I doing making suggestions as a lay person, to someone who has proclaimed to be an engineer?
Let this one go! The holes in the theory are wide enough to drive an 18 wheeler through.

Fwiw, your 6/12 pitch in the attic doesn't make a goddamn bit of difference. You're trying to rescue your original idea by inventing a hybrid!

I only mentioned the pitch because there's a lot of exposure to the sunlight and it creates more heat in the attic.
Still it seems like I would be ahead of the game. On a hot day I'm going to gain 50 degrees I think just by running the water through the attic. Remember most of the time it's just sitting there. I'm certainly not trying to replace a well manufactured solar water heater just looking for a lazy way to capture some heat.

 

[justoffal]

I think about before I insulated the roof on my metal shop building,, the temp gauge was reading about 145 degrees at the surface inside the building with an outside temp of 85 degrees,,

sometimes the problem could be it gets to hot and you need to run cold water to lower the temp,,

Yes I am amazed at how warm the attic gets even on an 80° day... I am very sure it's well over 100°.

 

[progressive hunter]

Yes I am amazed at how warm the attic gets even on an 80° day

the only downfall is showers that use the most hot water are usually done in the morning before it gets to full heat,, some people have put tanks in their attic to store hot water overnight,,

 

[justoffal]

the only downfall is showers that use the most hot water are usually done in the morning before it gets to full heat,, some people have put tanks in their attic to store hot water overnight,,

The tank would probably scare me I'd be afraid that it would spring a leak.... But it sounds like a great idea.

 

[Harpy Eagle]

Well the The PEX is about 50 bucks for that amount at home Depot. You would need at least four push to fit shark bite fittings.. The pex to copper are about 7 bucks a piece......and either a three-way valve or an extra T and two quarter turn valves. I don't know I'd say the whole thing is about 120 bucks. I have an older house so the pipe chase is a clear shot from the cellar right up to the attic.

That is not bad at all.

 

[justoffal]

That is not bad at all.

It probably wouldn't compete with a well manufactured solar water heater but I do think it might be worth 10 to 15% of the heat value at the very least.

 

[Woodznutz]

I've worked in and around the energy industry most of my life. I've met a lot of bright people both in the operations and design fields of my profession. It pays to network with people because human ingenuity tends to be more broadly applied if you have a greater number of inputs. Over the years I've collected a number of excellent suggestions that I put to use around my house to help with energy savings.

Here's one I'm thinking of trying so I'm throwing it out they had to see what anyone thinks about it. With the arrival of the new flexible piping called PEX many things are now possible that we're not previously possible.

A friend of mine put a copper to Pex take off on the input of his hot water heater running it up to his attic which is very hot in the summer. A three-way valve with a drain plug instantly winterizes this assembly. In the attic the pex runs along the entire side of the house hung on a steel rod as a long coil. It then returns back down to the cellar to the intake of the water heater having picked up 40 to 50° of heat from its original 65 to 70° city water supply. I'm thinking about trying this. Of course the peril herein is that the pex in the Attic could develop a leak and leak all over your ceiling. Still it seems like it might be worth a try.

Jo

Safer to run the PEX outdoors into a 'breadbox' solar heater and then into the water heater. Cheaper and no risk of water damage. The downside is that the PEX will greatly reduce water pressure, and you'll need a pretty long length of it to get any volume of hot water. Do the math on volume of pipes. I've experimented with 2" PVC pipe painted black and have had temps up to 120 degrees in about an hour in the hot sun. Good volume of water as well, and no scalding water to 'mix'.

 

[progressive hunter]

Safer run the pex outdoors into a 'breadbox' solar heater then into the water heater. Cheaper and no risk of water damage. The downside is that the pex will greatly reduce water pressure.

pex because of its smooth sides is the least restrictive of all the plumbing options,, so it will not reduce pressure and maintain a constant of what enters the house,,

 

[justoffal]

Safer to run the PEX outdoors into a 'breadbox' solar heater and then into the water heater. Cheaper and no risk of water damage. The downside is that the PEX will greatly reduce water pressure, and you'll a pretty long length of it to get any volume of hot water.

Yeah that's why I was thinking of the attic at least you capture some of the pressure back on the way back down maybe put in a vacuum breaker on the top of the downcomer. However that's not a bad idea...

 

[justoffal]

Yeah that's why I was thinking of the attic at least you capture some of the pressure back on the way back down maybe put in a vacuum breaker on the top of the downcomer. However that's not a bad idea...

 

[progressive hunter]

Yeah that's why I was thinking of the attic at least you capture some of the pressure back on the way back down maybe put in a vacuum breaker on the top of the downcomer. However that's not a bad idea...

pressure loss is not different than having a two story house,,

 

[justoffal]

pressure loss is not different than having a two story house,,

We have a pretty good system here even on the second story I have about 60 PSI.

 

[Woodznutz]

Two things:

1. I'd never run PEX in my attic as the stuff leaks at the drop of a hat.
2. It takes more calories to raise the temperature of HOT water than it does cold water!

You can prove that by putting both hot and cold water on your stove and seeing which one boils fastest!

Water increases temperature at the same rate within the range involved (40-120 degrees) with the same heat input.

 

[progressive hunter]

We have a pretty good system here even on the second story I have about 60 PSI.

not sure where some people come up with crazy things like pex leaks at the drop of a hat or it reduces pressure,, the truth of those two is the exact opposite,,

 

[progressive hunter]

We have a pretty good system here even on the second story I have about 60 PSI.

if you do do this you might consider using a larger diameter line like 3/4 or 1",, it will reduce friction inside the line and maintain a constant rate and pressure,, I learned this doing irrigation where you have to go long distances while trying to maintain the highest flow rate and pressure of the water,,

 

[toobfreak]

Water increases temperature at the same rate within the range involved (40-120 degrees) with the same heat input.

Well, if you really want to warm water, better to send it to the attic in copper pipe, that'll conduct heat faster than plastic pipe, and to really do it right, let the water go up into a glass covered splash tray so that it can pick up heat directly from the sun first before returning to the water heater!

 

[Woodznutz]

pex because of its smooth sides is the least restrictive of all the plumbing options,, so it will not reduce pressure and maintain a constant of what enters the house,,

Understanding PEX pressure loss

I'm having a new house built and the plumber just put in a parallel distribution PEX system. He put 3/8"s almost everywhere and I am trying to understand if it will be problematic. I have runs of up to 90ft, and an unknown rural city supply water pressure (60-70PSI?). The PEX design guide...

terrylove.com

 

[progressive hunter]

Well, if you really want to warm water, better to send it to the attic in copper pipe, that'll conduct heat faster than plastic pipe, and to really do it right, let the water go up into a glass covered splash tray so that it can pick up heat directly from the sun first before returning to the water heater!

thats a good way to talk yourself right out of doing something,, make it tens times more complicated than it needs to be,,