I have a Pentair Trition II Sand Filter (built before 1991) that came with the house I just bought. I'm currently fighting algae (kind of. I will be REALLY doing it once my TFT kit comes in - just stocked up on 32 gallons of 12.5% liquid chlorine) but I've noticed that I'm not building any real pressure on the tank even though it's running 24/7. A few days ago I accidentally cracked what I think was the original closure dome trying to fix a leak in the manual bleeder valve, so I replaced it as well as the dome o-ring and bleeder o-ring...
When I stayed at the house for three days in the middle of last month, the pressure gauge read about 14-15 psi the whole time I was there. The owner said this was normal, and that if it got up to 19-20 psi he'd backwash and all would be well.
At this point I'm reading between 11 and 12 psi, even during this algae fight (blue cloudy water right now, added about 30 gallons of bleach over the weekend and monday), I never see the pressure rise, backwashing runs "clean" for a few seconds, then cloudy for 60, then "clean" again, but the pressure on the gauge never changes.
I see no visible signs of leakage from the dome or bleeder, can't hear any hiss either (though not sure I would because the pump is right there) and whenever I open the bleeder valve - it pretty much never shoots water out, just sort of sputters air for minutes at a time.
I haven't the slightest idea what's going on here. Thoughts?