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Construction of distilled water runoff

January 30, 2020 — BarryK

This is the latest instalment of what is intended to become DIY plans for a solar water distiller. This is the previous post:

Now for the distilled water runoff. Water will trickle down the glass and at the bottom will flow into a channel, which will be on a slope, at the end of which will be a tube, taking water out to a collection bottle.

With earlier prototypes, an ongoing problem I had was the reluctance of the water to flow down the channel and into the tube. Water has surface tension, causing it to bead and stay where it is, then maybe subject to re-evaporation. To encourage the water to flow down the channel, it needs sufficient slope, of sufficient channel width, and sufficient pipe internal diameter.

What I chose for the channel is 10x10mm aluminium channel, 1.5mm thick, so the internal width is 7mm. from previous experience, I do not think it should be any narrower than this. Actually, I selected this channel as I already had it in the garage. I had purchased it from Bunnings, intended for an earlier prototype:


I think that there is silicone channel available on eBay, so that would be an alternative.

What I did was cut it so that it can be inserted into the distiller with maximum slope, and with a bent lip at the bottom end to encourage runoff into the pipe:


...on the right-end you can see the bent lip, and on the left-end the side walls have been cut, such that the channel is only 2mm deep at the very end. I used a very coarse file to rough-up the three outside surfaces, to optimise adhesion of the sealant. Here it is inserted:


...glued to the side of the distiller with silicone sealant. And there is one important detail -- the outlet tube has to be put in place first.

For the outlet tube I used 12x15mm silicone tube. This has internal diameter 12mm and outside diameter 15mm, so a 1.5mm wall thickness. Note, I had earlier bought 12x14mm tube from eBay, with 1mm wall thickness, which is OK but tends to kink very easily. The tube with 1.5mm thickness was purchased from here, AU$13.08 for 2 metres:


...for anyone building this distiller, 1 metre should be enough.

Of course, the tube has to be glued into the hole in the floor with silicone sealant, such that no water can seep out on the sides.

Here are some close-ups at each end:



To finish off, a plate has to be glued in front of the channel, to separate the water that is in the basin. Something fairly rigid is required, that will not absorb moisture and will tolerate up to 90 degrees C. It might be possible to use sheet silicone, with reinforcing glued to it, such as this sheeting:

However, I already had something from an earlier experiment. I had experimented with coating aluminium insect screen with silicone sealant, as reported here:

...that was a big area, but all that you need is a small strip of aluminium insect screen, about 50x670mm. I cut a strip off my big piece, and folded one side to give more rigidity. I also created small 90 degree flanges on each end, to aid with glueing.

I installed it in two steps. Firstly, glued it to the aluminium channel, with silicone sealant, held in place by a piece of wood, and allowed to set overnight. Next day, applied black sealant along the bottom. Here it is:


...the top edge is folded so is fairly rigid. Notice the height is almost the same as the wood frame -- there will be foam strips stuck on top, so the glass will sit about 4-5mm above the wood frame -- so there will be a gap for the water to flow down. Here are close-ups:



There is an air-gap underneath the channel, which will serve as insulation. Air will of course expand as it heats, and as it is completely sealed in, it will cause the wall made from aluminium insect screen to flex. Even at the runoff-end of the channel, I put plenty of sealant, so there is no air-connection with the outlet tube -- I did not want moist air getting into that cavity, as it would become a breeding place for pathogens.
I anticipate the change in air pressure to be OK, but could drill a tiny breather hole through the wood frame into the cavity, if desired -- think that is over-engineering though.

Shopping list:

Silicone tube 12x15mm x1m
Aluminium channel 10x10mm x1m
Aluminium insect screen 760mm x1m

...or scrounge a small strip of insect screen from somewhere, such as a scrap yard.

Stayed tuned for the next episode! 

Tags: nomad