Can Clogging Filters Cause Pump Basket to Fail to Fill Fully?

[nuttyp]

This surprised me and is something that will surely expose my ignorance of pump behavior and fluid dynamics. Can a clogging filter begin to reduce the water level able to be filled into the pump inlet filter basket? For all the detective-novel-like inlet leak detection threads I’ve read and contributed clever ideas to, I don’t recall a clogging filter mentioned as a possible cause. Maybe I missed it or maybe most had bubbles emerging from the returns so we knew air was getting in and we chased the source of an air inlet leak. In this case my buddy insists on continuously letting his nice inground 20K gallon pool get out of control. Well, it would be a nice pool if only he maintained it. Grumble grumble. Anyway, no return bubbles, but the cartridge filter psi rises soon after cleaning - 10psi just after cleaning the filter (or with no filter) and the basket fills nicely, soon then 25-30psi within an hour of reinserting (120 sq ft) filter and the basket struggles to fill fully. He has two pumps/two such filters, both exhibit similar behavior, not exactly but similar.

He fooled me I admit, claiming he had just cleaned the filters, could not figure out why the low level in the basket and observed reduced flow from a fountain. Then we thought about the cheap ExtremepowerUS $220 pumps (with no published pump curves), wondering if they are just junk. Then I cleaned one of the filters most carefully (strong jet nozzle) and the basket mostly filled. So I removed the filter from the housing and basket filled normally (10psi again on filter housing so we know filter was clean as it too was 10psi when freshly and carefully cleaned and inserted). All this even though the filter elements appeared rather clean before and after cleaning. Now we’re supposing sand from the sahara dust storms (visible evidence in bottom of the pool), perhaps also high combined chloramines that we need to test, and some unknown junky chemicals he got poolstored with are all rapidly clogging the clean filter, repeatedly. Got it, but……

Setting aside the out of control nature of his pool and all the things he needs to do to stop it, my (perhaps dumb) question is: “Are all pumps vulnerable in this way?”. Would it be the case that any pump may reach a certain amount of head and then start failing to fill the inlet basket? If true then perhaps many folks simply don’t notice it - not if the pump is powerful enough to overcome dirty filters until they get just so badly clogged, or with a pump so weak.

Thanks for any insights! … Joe

 

[PoolStored]

but the cartridge filter psi rises soon after cleaning

This is a typical indication of algae...even if you can't see it.

Algae is a result of not maintaining proper FC/CY relationship. Link-->FC/CYA Levels

I would do an OCLT on his pool. Link-->Overnight Chlorine Loss Test

He fails, time to slam. Link-->SLAM Process

 

[nuttyp]

This is a typical indication of algae...even if you can't see it.

Thanks @PoolStored. Invisible algae is a new one on me, but boy are you spot on. I told my pal his pool chemistry was an algae bloom waiting to happen - not to mention significantly acidic and other issues. Anyway, clear water when I tested, still clear yesterday, but 36 hours after getting the following test data the water is green as kermit the frog. When I tested we had: FC=0, PH=7.0, CYA=100+, TA=40, Calcium=275, WaterTemp=84,, resultant CSI -1.16. He dumped just one 2.5gal jug of chlorine in that day, but way too little too late, especially with TA=100. He did it to himself, I've been harping on him to test and curtail trichlor puck use when CYA above 30 or 40. But he won't test at all, keeps using the trichlor pucks, runs out of chlorine for weeks, not watching TA, and on and on. Just bashing my head against a wall - owner not compatible with pool ownership! I seem to find several of those type of folks, not sure how many times they need to learn the hard way. Lost cause and yet I try to help friends

But I'm still interested in the idea of the pump basket not filling due to cartridge filter clogging / psi rising. In case anyone wants to chime in on that front.

 

[1poolman1]

Thanks @PoolStored. Invisible algae is a new one on me, but boy are you spot on. I told my pal his pool chemistry was an algae bloom waiting to happen - not to mention significantly acidic and other issues. Anyway, clear water when I tested, still clear yesterday, but 36 hours after getting the following test data the water is green as kermit the frog. When I tested we had: FC=0, PH=7.0, CYA=100+, TA=40, Calcium=275, WaterTemp=84,, resultant CSI -1.16. He dumped just one 2.5gal jug of chlorine in that day, but way too little too late, especially with TA=100. He did it to himself, I've been harping on him to test and curtail trichlor puck use when CYA above 30 or 40. But he won't test at all, keeps using the trichlor pucks, runs out of chlorine for weeks, not watching TA, and on and on. Just bashing my head against a wall - owner not compatible with pool ownership! I seem to find several of those type of folks, not sure how many times they need to learn the hard way. Lost cause and yet I try to help friends

But I'm still interested in the idea of the pump basket not filling due to cartridge filter clogging / psi rising. In case anyone wants to chime in on that front.

Pumps do two things, they "suck" and they "spit." If it can't do one it won't do the other. In order to "fill" the pot it has to be able to remove all the air with a certain amount of waterflow that a very dirty filter, or any restriction after the pump, won't allow. Pump can't "spit."
Its the cause of the "My VSP has an air leak at low RPM" complaint.

A clogged skimmer basket, clogged pump basket, etc. will cause the, "I can't get any pressure" complaint, pump can't "suck."

 

[nuttyp]

Thanks @1poolman1. So simple and yet had eluded me. I had assumed, wrongly, they would still suck (fill the pot) and just make more pressure on the spit side. But if it can't eject the air with adequate water flow, it makes sense that the pot doesn't fill. I guess if it's bad enough with restrictions it can even prevent prime, or 'oscillate' prime where it may start to prime, then the resistance stops it, repeating. Good stuff.

 

[Jimrahbe]

Joe,

I have found that as my filter gets dirty, the larger the bubble gets under my pump lid.

I have a larger cartridge filter.. The smaller the filter, the more noticeable this would be..

Obviously, the problem is not the pump, nor the filter, it is algae.

Thanks,

Jim R.

 

[nuttyp]

I have found that as my filter gets dirty, the larger the bubble gets under my pump lid.

@Jimrahbe thanks Jim for reinforcing the issue! Simple and still amazing. Speaking of amazing, that CCPS520 of yours is quite a filter. Pricey too, but we all pay one way or the other