will this work?.. little advice please

[Bazzo]

Ok.. So I live in Spain, and get 300+ days of sunshine every year... My house is off-grid and we have a pretty good solar system installed.. (17x250w panels, Victron energy equipment and a good battery bank, backed up with a 10kva genset).. I want to heat my pool....
I have a 2ft wide wall around the property and I have worked out I can fit around 900-1000m of 25mm black irrigation pipe on top of it..(very cheap here and very UV resistant)

so, the plan is this...
A 50mm pipe from the pool pump housing for about 30m underground to get me to the wall... into a manifold feeding 2 x 25mm pipes to get me where I need to be on top of the flat wall, then each of the 25mm pipes into a manifold feeding 3 x 25mm pipes which will be about 150m long.. then back through a similar setup to the pump house.. I'm thinking this will spread the water over a greater surface area.. I worked it out to be about 23sqm of heating surface..(pool is 50sqm)

I don't want to run the filter pump all day long as its 1.5kw, so I was planning on running 2 smaller heating pumps, maybe 250w each, 1 to lift the water to top of the wall (2m) and another then to pump it around and back down to pump house... where syphon effect should then kick in an help?

What do you think.. will it work?
I don't want to lay out panels on the floor as we have dogs

[Mike90250]

I don't know if you can "series" stack water pumps, or if you should use a single pump of the proper size. You will also need at the high point of the system, some sort of air purge valve.

[Bazzo]

Good point about air purge.. Not thought about that.

[J.P.M.]

If you get the plumbing right and can handle the pressure drop right to maintain reasonable flow, no reason it can't work. Lots of DIY pool heaters around. Sounds like this one will just be 2 ft. wide.

[Logan005]

The wall sounds perfect, yes it can and does work, I have done similar. If the wall is masonry, you could just encase the pipe in a new cap of black stained concrete. mine was just under the black tarmac in our driveway. Works best in tropical to sub tropical regions. Bare pipe risk being damaged, but can also work.

[Bazzo]

Yes.. the wall is about 2ft wide.. it is 2.5m tall at the south facing rear of property so do danger of it getting damaged... was intending to lay along the wall then fix with straps at say 2m intervals to keep all in place.. 6 pipes out, and 6 pipes back.. each set of 6 separated so as not to draw heat away from the return with the supply..

My only concern is getting the right pump to lift the water that height without pulling too much power as I want it to run on a sensor.. so it only runs during daylight hours.. because of the solar.... .

[Logan005]

a small pump sized for the flow and directly connected to an over sized solar panel. something that starts slow as the panel gets early sun and pumps enough water to prevent over heat damage during solar noon to 2pm or so, then slowly reduces speed as the sun falls into the west. Many options on Ebay, and I am sure other merchants too.

[LucMan]

Most solar pool heating systems use the filter pump for circulating water through the panels because of the high resistance from the amount of piping used. I think that this is what you will need to do.
Running a 1 1/2 to 2 HP pump during the day is going to use a lot of of power. A couple of 200 watt pumps is only going to give you at most 3-4 gallons per minute if your lucky enough for them to overcome the total head of the piping. The pool filter pumps are capable of around 25 gpm, and capable of handling chlorinated water in an open system.
First step is to calculate total head for the piping system that you are proposing, then select a pump accordingly for the flow rate that will be required.
Pools only require a small delta T through the solar panels but high flow rate to circulate the massive amount of water in the pool.
No need for an airvent as the system is open on the outlet end where it will dump back into the pool, the water should push all the air out if the pump has sufficient power to circulate water through the loop.