I am converting a small bedroom into a wetroom with a high flow shower. i plan to have two hotwater tanks to provide for the extra water required and a solar water heater to help keep running cost down. i was also thinking about trying to recover some of the heat lost down the plug hole by using a heat exchanger just past the u-bend.
has anyone any experience of using one of these?
TIA
Steve
I couldn't find a UK source, in a few minutes of looking. For a shower, the design I was thinkinf of trying was a simple ring in the shower drain, past the strainer. This makes the water drain in a hollow cylinder, which flows onto the top of a coil of 15mm pipe. The water then flows down round the inside and outside of the coil, transferring heat as it goes (cold entry at bottom).
Shower drain is removable, and a brush can be used to clean off any accumulation of stuff from the coil, if needed.
A flooded heat exchanger could probably be much more efficient, in the same size, but suffers more from the likelyhood of clogs.
We had a discussion about this a while back over the idea of making a diy copy of an american device. The proposal was that a 30mm copper tube could be attached vertically to the drain, the incoming cold supply to the shower then entering the bottom of a 10mm copper tube, wrapped in a helix around the larger pipe and soldered to it, a neat contraflow heat exchanger with lots of other possibilities.
The outflow from the drain clings to the sides of the vertical copper pipe and transfers heat to the incoming cold supply. Thermostatic mixer valve then regulates the temperature by adding hot water.
AJH
Same basic idea - but transferring heat on both sides of the '10mm' coil, so that hopefully it requires less length. The tradeoff is that it's much more likely to clog on black water, so you need a filter - the other solution isn't any more likely to clog than a bit of pipe - unless you've got lots of grease going down it.
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