First cut at the construction of the DHW pond with the floating insulation slab.
The 2 inch thick insulation slab sits on top of the water surface.
On top of the insulation slab is (from bottom to top):
1) Layer of 6mil black poly
2) Water distribution manifold
The submersible fountain pump will sit in the pond, and pump water into the manifold when the sun is shining (and the pond is not already too hot).
Pic 1: The frame -- 4X8 ft. Total depth is 11 inches -- water depth is 7 inches.
There will be a separate frame for the glazing that sits on top of this. The glazing frame slopes slightly down from north to south (for drainage).
Maybe later a more steeply sloped glazing frame with a reflector to the north.
Pic 2: Frame with insulation installed.
One inch insulation on sides and bottom.
Pic 3: With the pond liner installed.
Liner is two layers of 6 mil poly.
Trying to do this with not penetrations of the poly liner for plumbing -- all over the top.
Pic 4: This shows the 2 inch thick floating slab in about the position it will be when the pond has water in it.
The edges of pond extend 3/4 inch above the top surface of the insulation.
The CPVC manifold is shown (there will be a layer of 6 mil poly under it in practice).
The submersible fountain pump is shown mounted off to the side, but in fact it will be in the pond.
The pump outlet will come up through the insulation where the blue marker circle is.
The connection from the pump to the CPVC manifold is made with flexible PVC tubing, so that the pump does not push the insulation slab up or down.
The centerline drains in the insulation slab have not been drilled yet -- I am thinking about bushing them with something like 1.5 inch PVC pipe to protect the insulation.
There is a valve in the pump outlet line which (I think) can be used to adjust the flow down.
Not sure if the pump will hold up to this, but willing to risk it -- not a very expensive pump.
Still concerned about EPDM sticking to Poly film when its heated by sun, and water has not yet started.
On prototype 1, the bubble wrap was so tightly fused to the Poly liner that they would tear before coming apart.
Going to try to leave a bit of EPDM on top of a bit of poly on top of a bit of insulation before we leave, and see if its fused when we get back.
I did a bit of a test on the CPVC full manifold on the deck yesterday, and I'm not sure that 2gpm is enough flow to get uniform output from the manifold. But, can try it, and see increase the flow some if need be. Or, block some of the holes in the manifold.
I should have made the manifold a bit longer. I am going to drill one 3/32 nds hole in the cap on the end of each of the manifold branches to try to get a little more water to the ends of the insulation slab.
I think that for the first go round, I am not going to hang the poly coils from the insulation slab. The manifold test on the deck seemed to indicate that the insulation slab is going to have to be very level to work, and I think that supporting the poly coils might distort it enough to make a difference. May just leave the coils out until the manifold is working. As you say, this may not be a problem when the top EPDM sheet is on, and some back pressure develops.
Any other changes??
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