Shower waste water heat recovery

[Tinbum]

https://thecodestore.co.uk/product/itho ... ery-shru60

a bit better-

[Paul_F]

https://www.cityplumbing.co.uk/Recoup-P ... m/p/475633 is probably a decent bet.

Fitting these for shower heat recovery is very under-rated: no moving parts or running costs, no maintenance required and they reduce demand for hot water by somewhere between a third and half meaning you effectively have a bigger tank which recharges faster.
Given that hot water is typically something like half of the heat demand for a well-insulated house and is delivered at higher temperatures (and so worse COP) than space heat, spending £500 on something which will reduce energy demand for heat by 20-25% is a no-brainer, at least for new build. Retrofit is a different story - depends a lot on where the pipes are.

[Ken]

This is chocolate teapot territory.

[Oldgreybeard]

This is chocolate teapot territory.

Not sure about that, to be honest. I've seen the data from the one a friend installed around 5 years ago, and it's pretty consistent. It increases the temperature of the cold water going into his hot tank by roughly 10 to 12 deg C, and that's a useful saving on the energy needed to heat his hot water. What's more, there's no good reason why a bit of kit like this shouldn't go on working for decades, as it's only a bit of pipe, really.

For a household taking four showers per day, with each shower using around 50 litres of water (5 minute shower at a modest 10 litres per minute), then that's a daily energy saving, in terms of sensible heat in the hot water, of around 2.5 kWh. If heated by a gas boiler with a 90% efficiency, at the current gas price of about 4p per kWh then that's a cost saving of about 11.1p/day, so the thing would pay for itself in about 12 years.

If the household was like my friend's, with two teenage girls that spend upwards of 10 to 15 minutes in the shower, then the payback time would be a lot less. Add in that this thing also reduces gas consumption for hot water for showers by at least 30%, and that this is pretty much a 30% reduction in CO2 emissions, and it starts to look like a very sensible thing to consider fitting.

[Gareth J]

An alternative could be to simply temporarily "store" the waste water somewhere so it could bleed off its heat to the building. Potentially as simple as a chambered tank. Maybe within an interior wall within a lump of concrete as a thermal mass. Potentially all warmish outlets could go there, bath, dishwasher, sink. Anything likely to be, on average, hotter than the house.

Challenge would be designing it to be cleanable! The design in my head has a roddable access pipe to outdoors.

[Tinbum]

An alternative could be to simply temporarily "store" the waste water somewhere so it could bleed off its heat to the building.

It's looking as if my house is easily going to exceed passive house standards as it is. During the summer their will be an abundance of PV so the cost won't be paid back and during the winter the waste heat will go towards heating the house. I could just make the pipe runs a bit longer inside the house.

Its an awful lot of money for what it is. A bit like server racks!!

[Tinbum]

Oh and on a bath you just pull the plug out when the waters gone cold.

[spread-tee]

I've unblocked a few of these over the years, it's not a pretty sight or cheap TBH. If the hot water demand is highish and access is good for maintenance it might be worthwhile. There's no such thing as maintenance free plumbing in my experience.

Desp

[AE-NMidlands]

I've unblocked a few of these over the years, it's not a pretty sight or cheap TBH. If the hot water demand is highish and access is good for maintenance it might be worthwhile. There's no such thing as maintenance free plumbing in my experience.
Desp

I think I might have "heard" you say that before - maybe somewhere else! Hence my reaction in post #6.
It's bad enough periodically cleaning out the under-sink manifold...
A

[nowty]

Oh and on a bath you just pull the plug out when the waters gone cold.

If it were me I'd drop my heatpump heat source exchanger in the bath until it had turned into a block of ice, then dump the ice outside.