You suggesting that not enough women air their views on here

Tom Foster can tell us about the benefits of cold showers
(I was in the sea on Monday, it is horrible and cold I can tell you, but not as cold as standing semi naked on a rock for an hour after)

Had to laugh at the idea of a timer on the hot water side of the shower system, turning off the hot supply after a set period had elapsed. But then, having given it some thought, and allowing my baser instincts to prevail, I could see the merit in it if linked to a video camera. The shriek followed by the crash of the shower enclosure door being flung open...!

Posted By: JoinerHad to laugh at the idea of a timer on the hot water side of the shower system, turning off the hot supply after a set period had elapsed. But then, having given it some thought, and allowing my baser instincts to prevail, I could see the merit in it if linked to a video camera. The shriek followed by the crash of the shower enclosure door being flung open...!" alt="" src="http:///forum114/extensions/Vanillacons/smilies/happy/rolling.gif" >

I had a similar experience a few years back when I'd forgotten about a scheduled power cut, which then occurred halfway through my (electric) shower resulting in having to rinse myself off in a dribble of cold water. You wouldn't have wanted to see it on video though.

look illegal to me sorry! water regs are very tight and dont allow any possibility of mixing new and used water-- is it fail safe?

Hi,
The main design consideration in these grey water recovery units has always been how to spread the flow such that it forms a layer down the inside face of the casing. The spray unit has to cater for many different flow rates and including soap etc slightly different viscosities and so forth. There is a tendency for it just to whistle down the middle. If you relay on a fully filled casing then you have a shell and tube heatX, and the usual equations would apply, failing that you have to get the max amount of the hot water spread out over the shell, and allow for a large amount of air in there.

Cheers, Mike up North

Tony -
I don't know if mine complies or not, but so far as I can tell it's similar to this unit which does:
http://www.itho.co.uk/service-support/literature/installer-manuals/shower-heat-recovery-60-installer-manual
(If the above fitted in our house, I would just buy it)

As to whether it's safe, and fail-safe - yes to both. It doesn't rely on anything I've made for safety, but solely on the 35mm pipe integrity. In the unlikely event of pinhole pipe failure, header tank cold would leak out via an air gap to drain.

It's much safer than the 2 coils in our DHW tank each of which have dodgy chemicals at the same pressure as the DHW water - so any pinhole here is very iffy, chemicals straight into DHW and you'd never know. 35mm pipe is thicker than 15mm, again safer.
As I mention, it's all from a tank in the loft, and not mains pressure so there's an air gap & can't affect mains.

ST - good comment, guess that's always an option if need be. Really rather not though, the power levels involved are very high (8-20KW, naughty shower), but the deltaT is very low (25C in winter expected)- so adding another heat exchanger in series won't do efficiency any good at all.

Anyway enough of the hand-wringing, here's a nice graph of my first test of performance. It's tested at an equal flow rate of 6litres/minute hot & cold into the two sides of the exchanger. Power saved is actually just power prevented from leaving the heat exchanger - whether it's heating up bits of copper or the cold flow, I class it as saved. That's why the power saved is very high to start with, then levels out. I get a steady state efficiency of 28% long term. To be honest, I'm a bit disappointed with the figure, I want more. I note the itho unit, when scaled back to the size of mine, achieves 50% - so that's my target!

Or just go for a batch process.

Batching would fit in a water but, including loads of insulation, it is only a couple of bath loads at worse, a couple of showers worth at best. Hole in the ground, for store not wife, you don't want to save too much energy

May it could be used in the 'WaterWall'

The problem with any DIY design of shower heat recovery system is demonstrating compliance with an acceptable standard, most probably EN1717 in this case. It's expensive to even get hold of the standard, let alone demonstrate compliance with it, yet failing to do so (or show compliance with another acceptable standard) is a criminal offence.

As you are required, by law I believe, to notify the water supplier when installing something like this it's hard to see how you could get away with pleading ignorance should something go wrong and the water supply become contaminated. The criminal penalties are serious enough that I'd not consider doing a DIY solution unless on a private water supply (the regulations are intended to protect the public supply, so don't apply to those with their own borehole or spring-fed supply).

TBH, I'm not sure. I believe the requirement to notify the water supplier is still there, and technically the legal issue appears to be over the separation of two classes of fluids (the regs divide fluids into 5 classes), and the water from the tank would still be in a much safer category than the water in the waste pipe.

Clearly a tank with an overflow outlet lower than the ballcock inlet would be an acceptable back flow prevention method, but the regulations still seem to imply that all fittings have to be approved, even those downstream of a tank, it seems.

Yes, historically taps in bathrooms could come off the tank in the roof but I dont know anyone who does that now. Finding a dead pidgeon in a customers loft tank certainly put me off the practice

Thanks for the heads up on dodgyness of installing this - TBH it's all a bit irritating that there may be no way around such that I can use anything homemade (my opinion of its safety is irrelevent, fitting a check valve doesn't get around the rules). So far as I can tell, every single water fitting must be WRAS approved, and even then approval must be granted for certain items (baths, bidet's, showers, pretty much anything that might use a lot of water - can't see a classification for this item). You might get away with an exchanger based on a pipe wrapped around a pipe, only insofar as you have two WRAS approved objects? Or maybe not, as simply rasing the temperature of mains cold over 25C changes its classification from "wholesome" to class2, which is dodgy in itself.

I'm going to ask my plumber what he thinks. He ought to understand WRAS & regs. There's even a free route to asking the local waterboard (Cambridge), so I'll try that too. I'm not holding my breath though.

We plan on installing a rainwater harvesting system for our house in the future, for DHW. I know that's odd, but our family suffers from exzema, and whilst we filter for chlorine, the water here is very hard (dries skin, bad for excema too). My understanding is that this would ONLY be a way out if the system were completely separate, and had no automatic tank fill from the mains (as is usual with rainwater systems). Gah.

Somewhat academically, I tweeked the heat exchanger by soldering a spiral of tinned 2mm diameter copper wire to the inner pipe, to make the cold water spin as it goes (cheeky copy of the itho unit, except they cut a screwthread into the copper pipe). It increased efficiency quite a bit, now it reaches a steady state efficiency of 50%. WooHoo :-(

Will report back if I get any joy with this :-(

I've been made aware of another player in this field - http://www.recoupenergysolutions.co.uk/

Seem to have a wider range of products that some of the other suppliers, with similar pricing.

They are SAP rated, but I can't seem to find any mention of WRAS approval. I'd be surprised if you could get a SAP rating for a non-approved product, so they are probably approved.

No affiliation etc.