Sand filter - flow question related to heater functioning

[jmccammo]

Hello all! Newbie here. I am not a pool owner, however I help maintain an older lady's house and yard and sporadically her above ground pool when I can. So I'm not experienced with pool maintenance and what to look for on the gauges, but I want to help solve her problem and know what to look for in the future. I'm not sure her pool's exact dimensions, about 4' deep by 20' diameter. But the question I have today is regarding her sand filter and mainly because of ongoing issues with her heater not running. She has pool people come over (i've never been there) but still they don't get the heater running. The pilot light is on and stays on. My theory is that the flow going through the heater is too low. She has a 1.5Hp pump and a good-sized Sparco sand filter, maybe 2' tall ball shape, which I'd guess is about 10 years old. It seems like there used to be more suction at the skimmer basket then there is now. The gauge on the filter is reading about 7.5 psi. It appears the "maximum working pressure PSI" is 35. But how about minimum pressure?? I didn't see a flow gauge, but the sticker says the design rate is 40gpm. The hoses seem about 1.5-2" in diameter, so i suppose I could do some math. But the 7.5 psi just seems really low to me, but like I say i'm inexperienced.

Assuming there is low flow, would that prevent the gas heater from kicking on? Yes, right? And would it seem that the sand filter would be the culprit? I have checked the hoses and appears there are no clogs.

Thanks for the help!!

Jared

 

[flyweed]

Yes, there are sensors in the heater...and if the flow is low, or non existent, the heater will not fire. This is a built in safety. 7.5psi, seems really low..you should backwash the sand filter, rinse, and then repeat the backwash procedure a second time..then put back into filter mode, and see where your PSI is at.

 

[jmccammo]

Yes, there are sensors in the heater...and if the flow is low, or non existent, the heater will not fire. This is a built in safety. 7.5psi, seems really low..you should backwash the sand filter, rinse, and then repeat the backwash procedure a second time..then put back into filter mode, and see where your PSI is at.

Thanks for the reply - I'll try this again and check the pressure.
Reading some more around here some more and sounds like if pressure is lower than normal (and I'm not sure that it is since I don't know the "clean" psi) then the problem is probably at or before the pump, which makes sense. Higher PSI would result with blockage after the pump. So I'll backwash again and I'll look in everything again and let you know what I find.