Recirculating Shower System

[Jeremy Harris]

  On 25/09/2019 at 20:46, Adrian Walker said:

 

OK.  If you use a waste water heat recovery unit, where are you going to put this energy?

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In the same place it would go for any installation, in the cold feed that flows to the DHW system, so it reduces the energy needed to heat the water used by the shower.

[Adrian Walker]

  On 25/09/2019 at 20:48, JSHarris said:

 

In the same place it would go for any installation, in the cold feed that flows to the DHW system, so it reduces the energy needed to heat the water used by the shower.

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Planning to use a Sunamp for showers & bath so connect the WWRU to the SunAmp cold water inlet?  

[Jeremy Harris]

  On 25/09/2019 at 21:00, Adrian Walker said:

 

Planning to use a Sunamp for showers & bath so connect the WWRU to the SunAmp cold water inlet?  

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Yes, that'll work fine, as the recovered heat will pre-heat the input water and so reduce the amount of energy that the Sunamp has to deliver.

[Adrian Walker]

  On 25/09/2019 at 21:20, JSHarris said:

 

 

Yes, that'll work fine, as the recovered heat will pre-heat the input water and so reduce the amount of energy that the Sunamp has to deliver.

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Thanks. I haven't had a chance to play with a SunAmp yet

[Jeremy Harris]

  On 25/09/2019 at 22:18, Adrian Walker said:

 

Thanks. I haven't had a chance to play with a SunAmp yet

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It would also work with a thermal store, hot water cylinder, or an instant heater, like a combi or multipoint, as it just reduces the amount of heat needed to reach DHW temperature.

[jack]

  On 25/09/2019 at 20:48, JSHarris said:

In the same place it would go for any installation, in the cold feed that flows to the DHW system, so it reduces the energy needed to heat the water used by the shower.

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For the highest recovery, you split the preheated water between the shower and the DHW cold feed. You can just supply it to the shower if connecting to both is difficult for some reason.

 

You can also supply it just to the DHW system, but from memory that's the least-recommended arrangement.

[Jeremy Harris]

  On 26/09/2019 at 07:31, jack said:

 

For the highest recovery, you split the preheated water between the shower and the DHW cold feed. You can just supply it to the shower if connecting to both is difficult for some reason.

 

You can also supply it just to the DHW system, but from memory that's the least-recommended arrangement.

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Is that running the pre-heated water back to the cold side of the shower thermostatic mixer, then?

 

That makes sense, as it as would probably be the most direct path for re-use of the heat.

[jack]

  On 26/09/2019 at 07:34, JSHarris said:

Is that running the pre-heated water back to the cold side of the shower thermostatic mixer, then?

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Yes, that was the de facto connection standard when I installed mine. I believe our plumber actually talked me into this arrangement instead of the dual connection arrangement (possibly due to pipework complexity - it's been a while, so I can't remember the reasoning).

[Jeremy Harris]

  On 26/09/2019 at 07:45, jack said:

 

Yes, that was the de facto connection standard when I installed mine. I believe our plumber actually talked me into this arrangement instead of the dual connection arrangement (possibly due to pipework complexity - it's been a while, so I can't remember the reasoning).

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The split system makes sense if the waste water heat recovery is also dealing with warm water from a bath, as well as a shower, perhaps.  That way the cold water replenishing a tank could be preheated, as well as the cold mix feeding the shower mixer being preheated for immediate use.

[Bitpipe]

Ultimately, what's the payback period for these types of technologies (include materials and labour) and the cost reduction over, say, 25 years?

 

I know some of them can nudge up the SAP by a few points but would expect that investing in a well insulated and airtight frame, decent glazing & external doors, MVHR, PV and an efficient  low temp heating system then further gains are very marginal.

 

I would lump rainwater recovery into that category - we were lucky in that we were able to build a very cheap DIY system due to spare space in our basement design vs burying a tank. My realisation is that even with 3500l of stored water, it doesn't last that long when used in the garden. Logically it is full when it's raining and empty when it's dry so only gives a bit of a buffer  - not much use during an extended dry period.  Would not use in toilets due to the potential health risks of using water containing bird poo microbes - unless you include an expensive filtering system.

 

Better in my view to use efficient taps, toilets and water using appliances. Again - once they are in use, what's the payback for installing an expensive grey water recovery system?

 

 

[Bitpipe]

  On 25/09/2019 at 09:11, Adrian Walker said:

Currently working with James & Emma on their self build house in Wareham and looking for a shower system.  Think that a Recirculating Shower System would be energy and water efficient and  Shower Loop System looks promising and open source too.

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Out of interest, how does the rest of their build perform from a low energy perspective? Are they building to a passive standard?

 

[Jeremy Harris]

  On 26/09/2019 at 08:24, Bitpipe said:

Ultimately, what's the payback period for these types of technologies (include materials and labour) and the cost reduction over, say, 25 years?

 

I know some of them can nudge up the SAP by a few points but would expect that investing in a well insulated and airtight frame, decent glazing & external doors, MVHR, PV and an efficient  low temp heating system then further gains are very marginal.

 

I would lump rainwater recovery into that category - we were lucky in that we were able to build a very cheap DIY system due to spare space in our basement design vs burying a tank. My realisation is that even with 3500l of stored water, it doesn't last that long when used in the garden. Logically it is full when it's raining and empty when it's dry so only gives a bit of a buffer  - not much use during an extended dry period.  Would not use in toilets due to the potential health risks of using water containing bird poo microbes - unless you include an expensive filtering system.

 

Better in my view to use efficient taps, toilets and water using appliances. Again - once they are in use, what's the payback for installing an expensive grey water recovery system?

 

 

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Just had a look and the Recoup unit recovers 67% of the waste heat (seems pretty good, I'd have thought 50% would have been doing well).  Assuming a 100 litre shower (ten minutes at 10 litres/minute, which seems pretty typical) at 38°C  and an incoming cold water temperature of 8°C, then the energy needed to uplift 100 litres of water by 30°C is about 12.561 MJ, or 3.489 kWh.  If all of the 67% of heat recovered is utilised by the shower, then it would reduce the energy needed for a shower from 3.489 kWh to about 1.151 kWh.  In reality there will be a bit of additional loss initially, as the shower and waste pipe warms up, so I'd guess that maybe 1.5 kWh might be a bit more realistic.

 

That's not bad, though, as if using an ASHP with a COP of 2.5 to provide hot water (probably about right for hot water production) then the electricity saved would be about 0.8 kWh per shower, so, allowing for holidays and assuming two people showering separately, the saving would be around 550 kWh/year.  At a unit price of around 15p that's an annual saving of about £82, which isn't bad. 

 

I can't find the price for these things, but would guess that they probably repay the investment within about 5 to 8 years, which seems reasonable for something that will probably last for decades.  Repayment would be quicker for a household that uses the shower more frequently.

[jack]

  On 26/09/2019 at 07:56, JSHarris said:

The split system makes sense if the waste water heat recovery is also dealing with warm water from a bath, as well as a shower, perhaps.  That way the cold water replenishing a tank could be preheated, as well as the cold mix feeing the shower mixer being preheated for immediate use.

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Not really - the system is really only functional when you have continuous warm water being used, and simultaneous warm water going down the drain. You might get a bit of recovery if you drained the bath while hot water was being used elsewhere, but realistically, it's designed and connected to work when people are having showers. I believe the split system works better because the higher flow of cold water though the device allows more energy to be extracted from the drain water.

 

  On 26/09/2019 at 08:46, JSHarris said:

I can't find the price for these things, but would guess that they probably repay the investment within about 5 to 8 years, which seems reasonable for something that will probably last for decades.  Repayment would be quicker for a household that uses the shower more frequently.

 

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They're not cheap - maybe £600-1000 depending on model?

 

In our case, we have a very active family who all do sports throughout the week. I sometimes have to shower twice a day, and my wife is the same. Our kids aren't that heavily into the long shower routine at the moment, but I'm sure that's coming. Overall, we foresaw the potential for a lot of heat going down the drain from showers. Even if the payback period is 15 or 20 years, there's an awful lot of energy being saved over that time, which is no bad thing.

 

[Dreadnaught]

Price example …

 

€440 from Austria inc. VAT. Haven't found a UK supplier.

 

https://www.rabmer.at/en/shop/produkt/zypho-izi-the-innovative-recovery-of-shower-heat/

 

[jack]

  On 26/09/2019 at 09:58, Dreadnaught said:

Price example …

 

€440 from Austria inc. VAT. Haven't found a UK supplier.

 

https://www.rabmer.at/en/shop/produkt/zypho-izi-the-innovative-recovery-of-shower-heat/

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The heat recovery on these smaller horizontal units tends to be a lot less than on the large vertical units (like this, for example).

[Jeremy Harris]

I've a feeling that we've discussed these before, as I've still got a photo of that green one here.  I remember looking at them, back when I was thinking of making a shower waste heat recovery unit (not hard to make, but the WRAS regulations on separation of foul water from potable water introduce some challenges).

[Dreadnaught]

Previous discussions (I take notes):

 

https://forum.buildhub.org.uk/topic/5187-shower-heat-recovery/

https://forum.buildhub.org.uk/topic/10061-working-out-a-scheme-for-dhw/?do=findComment&comment=171407

https://forum.buildhub.org.uk/topic/11509-recirculating-shower-system/?do=findComment&comment=193785

[Jeremy Harris]

Just found a price for the Recoup unit: https://www.cityplumbing.co.uk/Recoup-Pipe%2B-He-Waste-Water-Heat-Recovery-System/p/967757?isCustomerOnStop=false&siteName=City+Plumbing+Supplies&googleTagManagerTrackingId=GTM-NCL66X

 

~£641 inc VAT.

[ProDave]

I can see a heat recovery system working for a shower. All the time you are showering, cold water will be coming in, so the waste heat can be recovered either directly to the showers cold feed, or to the cold feed into the HW storage system.

 

But a bath?  Chances are while the waste bath water is going down the drain, there are no taps in use anywhere, so what is going to take the recovered heat away and to where?

[jack]

  On 26/09/2019 at 14:22, ProDave said:

But a bath?  Chances are while the waste bath water is going down the drain, there are no taps in use anywhere, so what is going to take the recovered heat away and to where?

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Agreed.

 

In fact, there's no reason to even have a bath drain routed throught this sort of unit. You connect the drains of one or two (I believe they recommend no more) showers to it, and connect the outlet of the device to the main drain. That's it.

[jack]

  On 26/09/2019 at 13:09, JSHarris said:

~£641 inc VAT.

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Not a bad price. I'm sure I paid more than that 4+ years ago.

[Temp]

£350 -£550 (plus VAT)

 

https://powerpipehr.co.uk/price-and-size/

 

 

 

Edited September 26, 2019 by Temp

[dpmiller]

One of the green ones arrived with me last week. At 311 euros inc vat I can justify the punt...

[Adrian Walker]

On my quest to save both water and energy for showers, I'm now looking at aerated shower head/systems.  Any one have one?

[Nickfromwales]

  On 28/09/2019 at 19:18, Adrian Walker said:

On my quest to save both water and energy for showers, I'm now looking at aerated shower head/systems.  Any one have one?

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Just fit a £2 flow regulator ( restrictor ) into any shower head and you’ll be “saving water” in seconds, without any premium. 

Edited September 29, 2019 by Nickfromwales