Separate pump for heater?

[PoolDoc]

I'll see if Al can look at this -- he's sorta the resident gizmo-guy.

[DrMacZed]

Awesome! Thanks very much.

[Poconos]

Welcome to the forum Scott.
First, if it isn't configured this way already it would be a big benefit to put the 400' in parallel. 4x100'. You can easily build 3/4 to 4x1/2 manifolds for the input and output. That would cut the flow resistance greatly.
Next, you may consider only diverting some of the water through the solar. Although theoretically from a heat transfer standpoint the more flow the better, you only need a slow flow, practically. I shot for about a 4 degree F rise in mine. My field heater is about 90 feet from and 10 feet above the equipment. It's 1200 feet of the 1/2 poly fed by 1.25" pipes and four 1.25 x 6x1/2 manifolds.
The problem you may have, and I do, is when diverting only part of the flow to the solar, if you get air in the solar system, getting enough flow and pressure to purge it. With only 5', when it is full of water you have gravity on the return side working with you so you don't need much pressure at the input to get flow. With air you need enough pressure to overcome the 5' rise to get started. This is easy to do by just diverting all the flow to the solar until the air is purged, then cutting back. If everything is totally airtight you should only need to do this when you open the system for some reason.
I don't know what you are using for a backing on the rack but since mine is laying on the ground I put a layer of black rolled roofing down first. Keeps the weeds down and provides a nice hot back surface.
Hope this helps.
Al

[PoolDoc]

Thanks Al.

Ben

[DrMacZed]

I had to read it a couple times But I think I am tracking now, took me a minute to wrap my head around what you were saying. So instead of the coil of hose I have now I should do something akin to the below as opposed to a single hose line. I can see now how the system you describe would be much less restrictive in terms of flow, a bit more labor intensive to build but it does make a lot more sense.

The verticals being the manifolds, and the horizontals are the smaller diameter hose.

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Thank you very much for pointing me in a better direction.

Scott