Is it possible for a pool heater to be partially clogged? I was just cleaning my filters and decided to put the hose in inlet of the heater. Most of the water comes back out, with some coming out the heater drain that I opened, and some coming out the outlet. If I try to put my hand over the heater inlet with the hose in it, it seems there's back pressure going through the heater. Is that normal, or should the water freely flow through the heater?
I was just wondering if heaters get clogged and need routine maintenance. I took off the water pipes going in and out, but am looking at the manifold cover wondering if I should take that off. From the manual, it looks like lots of stuff and gaskets underneath so I probably won't touch it for now.
I have a Starite heater, SR400NA, salt pool, pentair ccp320 cartridge filter, new 2-speed 2hp pump. Everything but the pump is about 6 years old.