The water test was performed on the heat exchanger module outside using the garden hose! The “maze” slowed down the water that it took well over a minute (nearer two) for the water to travel from start to finish! It did build up inside the channels but didn’t reach the top and overflow!

The waste trap did struggle to start letting the water through as it was in the horizontal position but after wetting it, it got going! There wasn’t enough head of pressure to bend the rubber seals apart and being brand new and dry, it was probably sticking together!

We increased the angle to see how much the flow changed and reduced the water level but in conclusion not a great deal! We were only changing it from a 1 in 75 slope to 1 in 40 slope .. 10mm drop to 18mm over the length (750mm) of the module.

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The Copper powder arrived and we mixed some together with some polyester resin and spread it out on a test piece of wood. After lunch it was not as conductive as we had hoped! It wasn’t the magic cure we were looking for to solve the problem with making a good thermal connection between the copper sheet and the copper pipes.

So throwing off our thinking caps, we decided, with the results of the water test in the morning, putting the copper pipe directly in the water flow inside the “maze” was the best solution at this time and place!

So we adapted the input and output pipes, drilled two holes in the copper sheet and threaded everything together, sealed all the new joints back up with the usual PU sealant and we wait (again)!

In the meantime we carefully lowered the drain pipe in the garden room’s floor to its lowest point to allow us the maximum range of tilt (up to a drop of 40mm) of the heat exchanger. Then we fitted the shower pump control box on the inner wall of the shower cubicle, connecting the electric and data cables through holes in the wall (sealed up!) and fitted short plastic pipes to the shower’s cold and hot water inputs, also going through the wall (also sealed up!).

Yesterday and today were spent on trying to get the copper pipes soldered to the copper sheet. But it was proving to be quite difficult with several factors playing against success! Like for example the flux was drying up during the heating up process and leaving “dirt” to stop the solder sticking to the copper. Pre-tinning the surfaces was tried but the heat required to melt the solder was also causing the already soldered joints of the U bends to come apart or at least breaking the joint and allowing potential leaks. We put on our thinking caps again!

The next trick to try is copper powder mixed with a binding agent (like polyester resin) and putting the copper pipes on a bed of this “paste” of copper and fixing everything down with silicone sealant. We await for the delivery of the copper powder!

In the meantime, we bent up the sides of the copper sheet to form the tray, cut two holes in the required places for letting the waste pipe water in and out. We also sliced up the soffit board (10mm thick foamed PVC plastic) into 45mm wide strips and “glued” them into the copper tray (using PU sealant) to form the maze like long winding path for the waste water to flow over the copper sheet while transferring the heat down into the copper pipes containing the fresh cold water (hopefully getting warmer!) running underneath the copper sheet!

We have also ordered a half dozen temperature sensors to monitor the performance of the heat exchanger and the “system” efficiency of the Shower as a whole.

Today we cut the copper pipes (474mm long), 17 of them, along with 18little (24mm) pieces, each to connect the two right angle bends (36 of them!). The whole thing forming a ladder like structure. This structure will be placed in close contact with the copper sheet.

The pipes are now soldered together but when we tried to solder the pipes to the sheet, the sheet started warping up! We think this is caused by the heat expansion differential of a local spot against the rest of the colder sheet. Our thinking caps are on!