Low pressure in my solar heat

[jackzach]

i put a homemade solar heater made out of 1/2 inch poly 300 feet of it. i have a 1/2 horse jacuzzi pump it will not suck very hard from the 1 1/2 hose from the skimmer to the pump that i reduced down to 1/2 inch poly tube. but when i put my filter on backwash,rinse,drain,jaccuzzi it draws normal from the skimmer and has normal pressure but when its put on filter (that puts it to the 1/2 inch poly it has very little return pressure and the skimmer will barely suck a fly down). please help

[czechmate]

You did not mention where is your solar heater placed. On the roof?
Your 1/2 HP pump is hardly able to negotiate any rise much above the top of the pool.
After all it is only little over 370 watts motor. Little more than in your kitchen disposer.
The impeller is not designed for this purpose and the 1/2 inch pipe is way too small.
Picture L.A. freeway shut down to 1 lane at 5 P.M.