using domestic water from GSHP loop

[bradenis]

We're designing a commercial 6 ton ground source heat pump system in Tulsa. Someone came up with the idea of designing the loop so that all of the building's domestic water was pulled through the circulating loop as well, presumably adding cooler water to the loop during the cooling season every time a tap is turned on. Sounds reasonable since all components are rated for potable water, but I've never seen it done. Any thoughts, concerns?

[jayguy]

i don't think i like it. can you guarantee the water quality if the ground loop breaks or gets a crack? i know it is high pressure, but still. you also would not know if you had a leak, (is it a leak or more usage?). even though the units may be rated for potable water, can they stand having no water stabilizing chemicals?

sounds like a great idea, but i do not think its very practical. maybe if you used a plate and frame heat exchanger or something, i could see it. also, wouldn't you be heating up the water? luke warm water from the cold water tap?

i am all for energy efficency. i hope you are doing this to gain WHEN POSSIBLE and not as part of the design.

[bradenis]

Thanks for the input. The ground loop would still be sized as normal. However, you make some good points for sure. Another I thought of was the remote possibility of a leak of refrigerant into the loop from the GSHP exchanger. Although that hasn't been a concern for desuperheaters on the other hand. Probably best that this idea only be used to possibly boost efficiency in a situation where large amounts of industrial process water were consistently being used, and potability wasn't an issue. Any other thoughts, experiences?

[jemawalton]

Just my humble two cents but I would be very nervous about crossing that street. Would it pass code? I can see a lot of finger pointing in the future if there are any problems with either system in the future. I would be sure to have a bypass installed for the domestic water in case of problems.

[ralphtheplumber]

Plumbing code violation.

If you want to transfer some heat between your domestic water and heat pump loop, that's fine, but you need a double wall heat exchanger.

[esornivram]

oklahoma water has high TDS/ silca issues as well as some acid/ low ph issues. have the water tested for its condition.
so they run water softeners, next most water coils ONLY LAST 6 to 7 years. these conditons corrode/ erode the inner tubes and cause ref. to water leaks, along with oils, and if this happens then your going to be in a world of mess. back flow/check valves are mandatory here in tennesse when this is done, I also highly recomment massive water filtration system on pre entry water into this application,
and pump and dump the waste water, and DONT dump it back into the well, if it does leak it could contaminate the well.
here is take 2 gallon per ton of water, so if you consideraation this then over size the well pump by 25 % at least or your house water presure suffers when the HP runs
lastly i would go with an seperate close loop system, 500 ft of water per ton, many drill well holes, and drop an double loop into the holes, but remember you will need an soaker hose to water, moisten the land/ ground an keep it moisten it during dry times, this can become an dailly thing, and when you forget then your cooling/heating suffers.

[Alf]

Not sure I understand your question. Do you want to use a vertical loop bore hole as a water well? If so, I don't think you have to worry about a code violation between the refrigerant and the water as much as the anti-freeze solution and the potable water. I think the idea has merit, however, how the local building code enforcement views it is a good question. Since 911, anything that comes into contact with potable water is suspect.