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Reminds me of this: http://www.chilipepperapp.com/ http://www.chilipepperapp.com/ I was thinking of installing a couple of these a few years ago, but didn't an

Reminds me of this: http://www.chilipepperapp.com/ http://www.chilipepperapp.com/ I was thinking of installing a couple of these a few years ago, but didn't and then forgot about them. It's a pump that gets installed near a faucet; you turn it on when you want hot water; it pulls water out of the hot pipe, sending it back into the cold pipe (where it circulates back to the water heater), until it senses that hot water has arrived, when it shuts off. As I say, I haven't tried it, but maybe I will — seems like an elegant solution, and works with existing plumbing.

Neil44 9y ago
It sounds like a good idea although some water companies are not that happy with an end user putting water back into the supply. Technically the pipe under your sink is open all the way back to the reservoir or whatever so there’s potential for system contamination there. Systems are usually designed so that syphoning cannot happen if there’s a temporary supply problem also. This is why cisterns are fed noisily from the top rather than quietly from the bottom.
- askvictor 9y ago
  A cistern could be fed from the bottom as long as there is a length of pipe going up (to the highest level of water) then back down. Or using a valve/backflow preventer.
  - Doxin 9y ago
    A length of pipe like that wouldn't prevent the supply sucking back water though. So that doesn't solve the whole contamination issue.
    - Neil44 9y ago
      Yes the pipe would need to rise from the cistern up to higher than the level of the resevoir, which would not always be practical. The resevoir would not then be able to fill the cistern over that loop :)
    - askvictor 9y ago
      Right you are; I hadn't considered that if the pipe is always full of water then gravity doesn't matter (as much)
- ovi256 9y ago
  There's a one way valve on the water pipe coming into in your home, precisely to avoid contamination. It's right before the water meter.
petre 9y ago
A better use for grey water is to store in a reservoir for flushing your toilets. You obviously need separate plumbing for collecting the grey water and for the toilets. There are also recirculation pipes for lung runs of hot water piping, like hot water columns found in hotels. The return circuit doesn't need to be thick, two sizes downwards will do (for instance a DN15 pipe for a DN25 column). Both the column and the return need to be properly insulated. DHW circulation pumps are usually made of brass and come equipped with a no return valve. This layout does exactly what you describe but instead of going into the cold water pipe, it goes back into the boiler.

Neil44 9y ago

It sounds like a good idea although some water companies are not that happy with an end user putting water back into the supply. Technically the pipe under your sink is open all the way back to the reservoir or whatever so there’s potential for system contamination there. Systems are usually designed so that syphoning cannot happen if there’s a temporary supply problem also. This is why cisterns are fed noisily from the top rather than quietly from the bottom.

askvictor 9y ago
A cistern could be fed from the bottom as long as there is a length of pipe going up (to the highest level of water) then back down. Or using a valve/backflow preventer.
- Doxin 9y ago
  A length of pipe like that wouldn't prevent the supply sucking back water though. So that doesn't solve the whole contamination issue.
  - Neil44 9y ago
    Yes the pipe would need to rise from the cistern up to higher than the level of the resevoir, which would not always be practical. The resevoir would not then be able to fill the cistern over that loop :)
  - askvictor 9y ago
    Right you are; I hadn't considered that if the pipe is always full of water then gravity doesn't matter (as much)
ovi256 9y ago
There's a one way valve on the water pipe coming into in your home, precisely to avoid contamination. It's right before the water meter.

petre 9y ago

A better use for grey water is to store in a reservoir for flushing your toilets. You obviously need separate plumbing for collecting the grey water and for the toilets. There are also recirculation pipes for lung runs of hot water piping, like hot water columns found in hotels. The return circuit doesn't need to be thick, two sizes downwards will do (for instance a DN15 pipe for a DN25 column). Both the column and the return need to be properly insulated. DHW circulation pumps are usually made of brass and come equipped with a no return valve. This layout does exactly what you describe but instead of going into the cold water pipe, it goes back into the boiler.