Flow rate increase: change solar from series to parallel

This is a followup to my posting about Power consumption of 2 spd pump. This post is not a question. Its intended to be my findings through testing and hopefully it will be usefull to others.

I finally got around to measuring the flow rate before and after changing my solar installation from series plumbing to parallel plumbing. The measuring was done with a 5 gallon bucket and a spare 1.5" pool hose help up against the "eye" return in the pool. I measured the number of seconds to fill the bucket, then converted to GPM. Formula was: 300/sec = GPM.

For comparison, included here is the flow rate when the solar is bypassed:

Low speed: 17.5 GPM
High speed: 43 GPM

A little bit about the "Solar Bear" panels I am using. From the Fafco website:

Maximum recommended flow per panel: 8 GPM
Recommended flow per panel: 4 GPM
Minimum flow per panel: 3 GPM

Series Setup:

Two solar bear panels, each 4x20. Those of you who have these Fafco panels know they have a valve in the header (red handle) that when turned "On", forces the water down 1/2 the panel to the far header, and then back down the other 1/2 of the panel. The water effectively makes 2 trips through each panel. Since I have 2 panels, my water was making 4 trips through those very small tubes. Since a picture is worth 1000 words, here's a doctored marketing pic:

With this setup, the flow I was getting was:

Low speed: 11.5 GPM
High speed: 27 GPM

In this setup, I'm clearly pushing more water than recommended through those panels, even on low speed. And the low speed is inadequate to clean my pool in 10 hours time.

Parallel Setup:

So I re-plumbed to parallel flow by connecting the bottoms as the inlet of the panels, and the tops as the outlet. I then turned the red handle to the "Off position" to allow water to flow through the bottom header. Instead of the water making 4 trips through the panels, now it makes 1 trip. Now I'm getting:

Low speed: 15 GPM (30% increase over series plumbing)
High speed: 30 GPM (11% increase over series plumbing)

Now I am no longer using the panels in their recommended configuration. I am pushing water through the tubes only 1 time, instead of 2 (as designed). So lets say for arguments sake, I can double the recommended flow rates. Now, on high speed, I am just within the max flow rate. And I'm getting a much more reasonable low speed flow too.

Lessons learned:

- Plumb multiple solar panels in parallel.
- Don't use a low head/high flow pump for long pipe runs and solar.

My remaining question: Will I have enough GPM on low speed to install a SWCG? 15 GPM seems a little low.

And since everyone asks for pictures....

Jason M