Filter PSI seems low...

[VTSoundman]

Quick question: Recently purchased a home with pool (see stats below). Just cleaned the filter cartridges of the my Sta Rite 3 300sqft dual cartridge system - and they were really nasty. Maybe 1.5-2 yrs since they were last cleaned. Cleaned cartridges, Overnight/15hr soak in Cascade, look pretty good with some minor staining near top. Skimmer is clean. Removed the diverter (it floats) and PSI did not change.

The PSI prior to cleaning was 15 (then spiked to ~22 after fixing some pump wiring).

The PSI after cleaning is 6-7 PSI (new gauge)/zeros when off.

Filter is 1/2 HP single speed Sta-Rite PE5C-180L. Lines in and out of the filter 2". When the booster pump is running, it drops by about 2PSI. Skimmer & drain lines are 1.5" copper. Return line to the pool is 1.5" copper. Two returns in the pool, both appear smaller than 1.5" (haven't measured them yet) - no fittings.

All lines in ground are copper (old pool - 50 yr+!)

Flow:
1.5" Skimmer/Drain - Pump - 2" Check Valve (broken spring, but open) - 2" Inlet/Outlet Canister Filter - 1.5" Heater - 1.5" to Returns (With 3/4" split to Booster Pump).

Question: Is the main pump motor undersized? Is my filter PSI too low?

Mike

 

[jblizzle]

There really is no such thing as undersized or too low of a pressure ... assuming you have good flow and everything is working. Those of use with 2-speed pumps running on low may only show 2-3psi on the filter if anything at all.

Does the flow seem more or less than you have previously observed?
The only way for the pressure to be lower than it should be would be to some suction clog or a clog between the pump and filter, but I am not sure you have a problem at this point ... just a nice clean filter with a small pump.

 

[VTSoundman]

The pool is new to me, so flow being 'ok' is not a subjective judgement I can make :-D

From other pools I've owned, the flow seems low...
This is a single speed pump system. I've ordered the flow meter from TFT...so we can find out for sure!

I will be installing a timer to cycle the main pump on/off multiple times per day - on for 2 hrs, off for 6.
The pressure pump will run for about 2 hrs/day.
I'll start here and go up/down depending on need.

 

[jblizzle]

Did you notice a good increase in flow from the dirty filter to the clean filter?
We recommend cleaning when the pressure rises 20-25% over the clean pressure. So in you case this would be around before 9psi ... well before the 15psi you previously saw.

Again, I think it is just a small pump with a properly large filter.

If the future if the pump goes bad, you could consider getting a little larger 2-speed pump and run on low most of the time, but have the option of more flow for vacuuming, skimming, etc if so desired.

 

[VTSoundman]

Just as an update, I installed the flow meter. Having cleaned the filter about 2 weeks ago now, the flow rate is about 45GPM.
Assuming a 20k gallon pool, I'll need to run the pump for about 7.4 hrs for a single turn over. Seems a little slow, doesn't it? I've read that 1.5-2x turn overs per day is suggested. That means about 11-15 hrs of pump time...seems high.

I've not had the pool long enough to see the filter become clogged again (newly purchased home)...The flow metere was not installed prior to cleaning the pump either.

Any thoughts on the flow rate? The pump and copper plumbing are pretty old...(plaster pool was built in '65). I'd just like to know what I have to do when the time comes to update during the pool remodel.

 

[mas985]

I would ignore those turnover recommendations as they will lead you to running your pump way too long. Most pools can get away with much less than a single turnover per day and usually 3-4 hours of run time on full speed is enough.

45 GPM is not totally unreasonable for a 1/2 HP pump. It could be you have high head loss plumbing. What is the filter pressure?

 

[VTSoundman]

Thx for the quick response.

Filter pressure with only the main pump is 8PSI (lowest was ~6PSI after cleaning 2 weeks ago).

The old 60PSI gauge was replaced with a new 30PSI when I cleaned the filter. I don't have a reason to think the new gauge is faulty (reads 0 when off).

When I turn on the booster pump for the krauly legend, it drops to about 5 PSI. Interestingly enough, the flow gauge does not really change when I turn the booster pump on.

It could be there is high head pressure - there are only 2 returns in the pool and they appear small. All of the plumbing (except for a few feet around the filter) is copper.

The pump/filter is physically located about 10-15' from skimmer is about level with the pool. The returns are adjacent to the skimmer - located about 6' on either side of the skimmer - or about 10-15' from the pump. The Krauly connection is located mid-pool - perhaps another 15' or so from the skimmer for a total lenght of about 30' from the booster pump.

Regarding the turn over - I was going to low ball with 2 x 3hr runs per day and see what happens...and drop it to 2x 2 hr runs per day in the winter.

 

[mas985]

The pressure seems a little low too which could indicate a suction side problem. But it could also be normal if the suction side head loss is high.

Did the pressure ever read higher than 8 PSI?

Do you have any air in the pump basket?

What is the size of the suction side plumbing?

Is there only a single suction run to the pump?

A simple thing to check is to remove the pump basket and see if there is anything in the impeller inlet.

Otherwise, it might be worthwhile taking apart the pump to inspect the impeller.

 

[VTSoundman]

Hi -

Only time the pressure was high was prior to cleaning...from my original post:

The PSI prior to cleaning was 15 (then spiked to ~22 after fixing some pump wiring).

The PSI after cleaning is 6-7 PSI (new gauge)/zeros when off.


Pump basket has no bubbles or air...only a single suction line to the pump (with a diverter in the skimmer for the drain). I will check the inlet this weekend and report back if I see anything.

Thx for the help!