Shower size, 6 kW really? Seems a good shower.

[Madrab]

You would surely use copper for this job.

It could be a copper pipe or a coil for sure but if it's DIY'd who knows. Just asking the question.

Ah .... Just seen one @ city plumbing called a recoup that looks similar and it's an internal copper jacket HEX.


Every day's a school day

 

[cdbe]

It's a commercial product made by a company called Recoup, it's a copper "hex" inside. Unfortunately they were £600 at the time but I bought them off eBay for £80 each.

Regarding my "constant hot water" if my hot water is timed on, my 145l cylinder is up to temperature, my shower is 8l/min, my boiler is 15kw and my recoup is pre heating the cold into the shower I recon I could shower for hours without running out.

The only, not very scientific thing, I can say about the recoup is that my ensuite whb cold tap is fed from the shower cold feed and if I step out of the shower and run the tap then fairly warm water comes out.

 

[Why Not Indeed]

This looks like it:

Recoup Pipe HEX - Vertical waste water heat recovery for showers

Recoup Pipe HEX WWHRS, NEW waste water heat recovery system for showers. SAP listed, high efficiency, competitive price and easy to install

recoup.co.uk

 

[Harry Bloomfield]

Ah .... Just seen one @ city plumbing called a recoup that looks similar and it's an internal copper jacket HEX.


Every day's a school day

The idea of that one, seems to be a sort of centrifuge. The incoming cold, is caused to swirl its way along the warm drain pipe in the centre. It would take a long time, for it to recover £600 worth of heat!

 

[Why Not Indeed]

I notice that @cdbe doesn't seem to have his attached, maybe that's why he got it at an 85% discount

 

[Madrab]

Regarding my "constant hot water" if my hot water is timed on, my 145l cylinder is up to temperature, my shower is 8l/min, my boiler is 15kw and my recoup is pre heating the cold into the shower I recon I could shower for hours without running out.

Ah I see what you mean, well theoretically yes but it all comes down to the cylinder recovery - coil output, CH flow temps, cw temp etc.

If all that was set up correctly then I guess it could be self sustaining at certain times of the year. As suggested it would be interesting to see the delta's on the mains, compare to the waste temp delta's just to see how efficient that recovery system was. They claim 50% efficiency on system B @11L/min @ 40Deg.

Again though - a gain is a gain is a gain and if it saves energy then all the better.

 

[cdbe]

I notice that @cdbe doesn't seem to have his attached, maybe that's why he got it at an 85% discount

It is, they are a pain to fit because you're supposed to used all the bends supplied for optimum performance. That one's in the garage, the other one is in the utility under the ensuite.

 

[Why Not Indeed]

I doubt you'd ever recover the installation and manucturing energy needed to install heat recovery from a drain. The waste from a shower isn't very warm, as it gets blown through the air, just like a cooling tower in fact.

I think you're probably right to be sceptical about the ROI. Hard to find much obviously independent information on ROI for these systems. Only a handful of manufacturers.
I think cdbe is a "best-case" for retrofitting - he did it himself, he didn't have to rip up his house to do so and he got the key component at a hefty discount.
Lots of relevant comments here:

Waste Water Heat Recovery Systems - TheGreenAge

What is a WWHRS and how does it work? Typically, a waste water heat recovery system works by extracting the heat from the water your shower or bath sends down the drain. This heat is used to warm the incoming mains water, reducing the strain on your boiler and the energy required to heat your

www.thegreenage.co.uk

 

[cdbe]

I think at the time you could get some SAP points if fitted in a new build that presumably justified the ridiculous cost.

 

[Ivor Windybottom]

Greenwash

 

[Harry Bloomfield]

Lots of relevant comments here:

Waste Water Heat Recovery Systems - TheGreenAge

What is a WWHRS and how does it work? Typically, a waste water heat recovery system works by extracting the heat from the water your shower or bath sends down the drain. This heat is used to warm the incoming mains water, reducing the strain on your boiler and the energy required to heat your

www.thegreenage.co.uk

Which says, other ways to save - 'That means less time in the shower, fewer baths and using a dishwasher instead of washing up under running hot water.'...

Who in their right mind, washes up under a running hot tap? Usual routine here, is - Rinse off under a cold tap if necessary, wash in a bowl of hot soapy water, rinse soap off quickly, under a dribbling cold tap, then in the rack, to drain and dry. A cloth, is never used..

 

[Ivor Windybottom]

I'm imagining the energy involved in extruding molten copper, moulding the plastic and assembling the whole thing. How much of this would be recovered in its lifetime?