Low Filter Pressure, High Flow Rate... Could It Be Dog Hair in the Filter?

Spacesuit

New member
Jun 23, 2018
3
OKC
Long time lurker here... need a hand with this one!

Bought a new (to me) house in April. Has the same Sand Dollar filter as my last house, but base pressure is a little higher (15 PSI instead of 9 PSI), so I figure the sand is a little older. Has been fine up to today. When the PSI reaches 25 or so, I backwash back down to the base level. No problem.

HOWEVER, today I notice that the filter pressure is holding at 5 PSI (10 less than normal). Skimmer basket is clean. Pump basket is also clean. Impeller turns and is clean, as far as I can tell (used fingers and a screwdriver to check for debris). Suction beneath the skimmer basket and return pressure out of the eyeballs are both STRONG. I also detached the inflow pipe on the top of the filter to have a quick look at the inside of the valve, and it's clean in there. Detached the outflow pipe from the pump for a quick look inside. Clean there, too. Pool water is clear. Tried backwashing and rinsing the filter (3min / 30sec) which made no difference... still 5PSI. Drops to 0 when turn the pump off. Gauge is new as of April. Pump seems to prime as normal. I don't see any water leaks around the filter.

The only thing that I can think of is that a dog got into the pool two nights ago and there was some matted hair floating on the surface. We removed most of it from the surface with a sweep. I would think that dog hair in the filter would INCREASE pressure, and that it would resolve when the filter is backwashed?

Any help is very much appreciated!
 

kevinskii

Gold Supporter
Aug 6, 2019
96
Los Angeles, CA
A couple of possibilities I can think of, not owning a sand filter myself:
1. You did a great job backwashing, hence the low psi, and everything is fine.
2. Maybe more likely: It's a really old filter and you broke some internal baffling during the last backwash, hence much of the inflow is bypassing the sand.

I don't see how the dog hair would be a factor. Can you open the filter and inspect it?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,930
San Dimas, CA (LA County)
The only way dog hair would lower the pressure is if it's all tangled up around the impeller. You say the flow is strong, so that's not likely it. Any valves get moved? Any eyeballs get popped out? I'm out of ideas.
 

Spacesuit

New member
Jun 23, 2018
3
OKC
1. You did a great job backwashing, hence the low psi, and everything is fine.
Hoping that this is it. The pool has remained clear so far. Not planning on opening the filter beyond the quick look at the multiport unless things start getting cloudy. Just weird that it's 8-10 PSI lower than normal.

2. Maybe more likely: It's a really old filter and you broke some internal baffling during the last backwash, hence much of the inflow is bypassing the sand.
Really hoping this is not the case. I'm not seeing sand from the returns. The filter isn't super old—maybe 3-4 years?

The only way dog hair would lower the pressure is if it's all tangled up around the impeller. You say the flow is strong, so that's not likely it. Any valves get moved? Any eyeballs get popped out? I'm out of ideas.
The multiport valve seemed OK when I looked inside it through the inflow. Turned it a few times and it looked clean inside. Eyeballs are in place. Going to triple check the impeller today.

Thanks for the help—going to keep an eye on it and will report back if I get to the bottom of the pressure issue.
 

JimMarshall

Gold Supporter
TFP Guide
Jun 5, 2017
1,003
Oil City PA
I know this probably isn't the project you want to tackle, but you could open the filter to check on it and give the sand a deep cleaning while you are in there, being a new to you house and you not totally knowing the history of the filter. It would give you some piece of mind. Plus opening the filter to check and repairing if necessary is less work than opening it to repair AND having to fix your water after it gets away from you.
 

Yev

Well-known member
Jul 29, 2014
547
Independence, KY
Zero chance about dog hair being the cause.

Maybe channeling inside of the sand? If you somehow managed to create a path of low resistance in the sand, then this would explain it.

And a deep clean might be a good time to inspect.

Any chance you have a multispeed pump?
 

Spacesuit

New member
Jun 23, 2018
3
OKC
Wanted to report back in case anyone else experiences a similar problem. Turns out it was a faulty gauge! My water remained crystal clear—but the pressure (according to the gauge) eventually dropped to zero. So... I installed a new gauge today and the mystery was solved! Back to 14 PSI. I made sure to flush out any nasty by letting water flow through the gauge fitting before installing the new one.

I'm still planning on a deep clean of the filter at the beginning of next year's swim season.
 
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