Recover gray water energy

[rodolpheb]

Hello,

I'm looking for a water-water heat pump that would be able to recover the energy contained in gray water to heat a hot water tank.

Volume of the gray water collector to be sized according to the heat pump.

Thank you for your contribution.

[Ahmed]

It is tempting to recover energy which then appears as "free": it is an error of reasoning, because all energies are free, only their exploitation is expensive.
In your case, the volume of gray water is low compared to the installation required (and to heat only one water heater ...).

To realize this, examine what your annual consumption of hot water costs you and you will see (not to mention the technical problems) that it is very difficult to hope to reduce an operating cost by an investment cost , on a small volume.

[moinsdewatt]

Do you have such a gray water flow to make it worth it?

The achievements mentioned in the press relate to installations whose gray water is gray water from buildings.

[Remundo]

the simplest ... have a tank that lets the gray water cool in the house. In practice it is almost naturally done in the pipes, the time that it passes.

even install a heat pump, as much as it is air / air or air / brine.

[Christophe]

+1 with remundo, it would be much simpler to install a buffer tank (a few hundred liters?) In the cellar or the crawlspace ...

A good design of this tank (modeled on septic tanks all waters?) Would avoid having to clean it too often (hair, soap ...)

ps: a study to (re) read https://www.econologie.com/economie-d-en ... -3985.html

[Ahmed]

Septic tanks are not designed to avoid the deposition of materials, on the contrary; it would therefore be better to provide well-studied devices in order to facilitate the inevitable cleaning * of this system which promotes fouling, since it slows the flow ...

It remains to be seen whether the game is worth the effort.

* Maybe that’s what you meant, Christophe?

[Christophe]

Uh, the pits are designed so that after a certain time of stagnation (biological action), the "purified" water, generally more liquid than "what happens", is evacuated.

It was the idea I had in mind: a buffering + a "cleaning" access as in well-designed septic tanks ...

I have been in a house with a pit for 7 years, I have never had to empty it ... never smelled an odor either, proof that it works "well" (I do not use chlorine, bleach ...) so a well designed gray water buffer system could also work well for years without any maintenance!

[Ahmed]

With the difference, as you note well, that the septic tanks or all waters use this time of stagnation to biologically reduce the mass of matter, whereas in the case which occupies us here, this time, shorter, is not spent than heat exchange.
This delay will necessarily be accompanied by sedimentation, without the reduction phenomenon (even if these waters are, by definition, less charged than in the case of pits).

[Did67]

All-water pits also accumulate sludge ... There is always a part of "molecules" that the bacteria are unable to dismantle!

7 years without it getting blocked does not mean that there is no problem, that the volume is not reduced by half, or even more ... or that it will last forever!

The accumulation of this sludge has two consequences:

a) currently, the active volume is already reduced, the passage time in the pit reduced and therefore the pollution less well treated

b) sooner or later it will malfunction

[I say that and it's been half a dozen years since I last vacuumed the bottom either!]

[Did67]

Do you have such a gray water flow to make it worth it?

In fact, it is a question of first evaluating the "calorie deposit":

a) the volume of gray water X their temperature (shower water at 38, dishwasher water at 50 or 60, washing machine water at 30, 40, 60 or 90 ...)

b) the distance between the connections: as a general rule, the water leaving the 38 ° shower will reach a lower temperature ...