What's clogging my cartridge filter?

[CurtisT]

I have a sta-rite system 3 cartridge filter that is needing to be cleaned about once / week. Last Friday morning, I cleaned both cartridges with a hose. There was minimal heavy stuff (grass, dog hair etc... the dog doesn't swim in the pool but some blows in)... mostly kind of a bluish "dust". Of course, even after cleaning, there is the usual gunk between the pleats still, but pressure dropped to 9 PSI and went up to about 13 PSI within a few hours (as the cartridge got re-saturated with water?). The water has remained crystal clear since then and the only thing I've added is bleach and PolyQuat. However, I just checked and the pressure is now up to 18PSI again, so it will likely be 10 PSI higher than "clean" within a couple of days.

Does anyone have any idea what could cause this? There is a tree hanging over the pool, although at the moment it's not dropping a lot of garbage. The filter is 1 year old, but my pool turned black with the hurricane and again this spring with a heavy rain and was having to be cleaned 3-4 times per day for a while. Also when the tree drops pollen in the spring, it clogs up really fast. Is it possible that with all of the extra cleanings, it has worn out this fast?

It generally looks to be in good shape. one of the plastic bands was coming lose so I hot glued that back on and it has a rust stain near where the inlet pipe is.. other than that it looks pretty good, although I may not know what to look for in a worn out cartridge.

 

[duraleigh]

If you'll post a set of current test results, we can help. Without them, it is simply guessing.

If you have added something very recently since the test results, let us know that.

 

[CurtisT]

Here are my results from the 2nd. (I cleaned the filter on the 3rd)...

(all results are from my own testing)
Total Cl = 2.5
Free Fl = 2.5 (now 5+ .. that's as high as my test kit goes... the only Cl I've added is bleach until I turned the tab feeder back on yesterday in preparation for vacation - I've fed in about 1/2 tablet so far)

pH = 7.5 (tested that again this morning and this is still where I am)
Alk = 145
Ch = 190
CYA = 65-ish

Water looks crystal clear and no sign of anything growing in the pool. The only thing I've added since the tests is 1 qt of Muriatic acid (trying to gradually work the Alkalinity down a bit but don't want to add any more right now since I'm heading on vacation tomorrow).

 

[Bob_Funk]

I do not know what is clogging your filter but your chlorine was to low, with a CYA level of 65 your MINIMUM fc chlorine is 5 & you want to shoot for a level of about 7 or 8

pool-school/chlorine_cya_chart_shock

 

[Guest]

have you ever acid washed the carts without degreasing them first?
Have you used any clarifiers in the past few months?

 

[CurtisT]

Last fall, I did give it a TSP bath after rinsing off the heavy stuff. Would that constitute an acid wash? I did put in clarifier a couple of months back after a storm turned the water black on me. I've quit using them now, however I did use them on a weekly basis for about a year on the advice of my pool builder.

 

[duraleigh]

It's a little unclear what the issue is but reading your posts, you seem to have been using things other than chlorine to keep your pool clean. You don't need or want things in your pool that are unnecessary.

I would get the filter very, very clean and then shock the pool up to 25ppm with chlorine only and then hold the chlorine at that level for 24 hours. During that time I suspect you'll have to clean the filter at least once or twice again.

Next, keep your chlrine level between 5-8ppm all the time. Your CYA is already high at 65 and I would discontinue use of the pucks.

 

[reebok]

I do not know what is clogging your filter but your chlorine was to low, with a CYA level of 65 your MINIMUM fc chlorine is 5 & you want to shoot for a level of about 7 or 8

pool-school/chlorine_cya_chart_shock

I don't think he's following this method based on polyquat use.

 

[CurtisT]

I am using the bleach, but decided to use the Polyquat as a backup since I'm heading out of town and don't know what will happen to my Cl levels while I'm out and running on the auto-feeder. Also, I was having a hard time keeping chlorine up when we were running 100+ degree temps and zero clouds the last few weeks (the overnight tests were keeping chlorine, but the sun would just burn it off once it came up during the day). Now that we've gotten some clouds the last few days, my level has been staying up around 5 without too much problem. When I get back from vacation I can start trying to elevate my chlorine levels, but I'll probably still keep polyquat in the pool at least through the summer because the sun down here can eat chlorine so fast.

But I guess that's all a whole separate discussion.. I just cleaned the filter again and back down to 10PSI... we'll see how it goes.. It really didn't look that dirty when I opened it, but cleaning it left kind of a grey-ish slime on the ground.

 

[Guest]

What you are filtering out is dead algae. It is going to continue to happen until you either lower your CYA or raise your FC. Because of the low FC and high CYA you are living on the edge of a nascent algae bloom that the polyquat is helping control.
Try keeping your FC at about 8 ppm for 2 weeks and see what happens.
You also need to upgrade your test kit. Which kit do you have now? Depending on what you currently have you might be best served by replacing the entire kit or just upgrading the chlorine test.

 

[CurtisT]

Thanks. I had initially assumed that the stuff might be algae, but then when it kept clogging after the water was clear, thought it might be something else. I'll give that a try when I get back from vacation and see what happens. My test kit is the Taylor K-2005 with the standard DPD kit.. I'll probably pick up a FAS-DPD soon as well.

I had a whole question about potential health effects of higher chlorine levels, but I'll post that as a separate thread I think.

 

[CurtisT]

Well I returned from vacation and the filter pressure held with only about a 1 PSI rise! I shocked the pool when I left for vacation and the chlorine was maintained at about 5.5 while I was out of town. I think you were right about the algae. In retrospect, although I was getting no overnight chlorine loss, I was using it pretty heavily during the day for a couple of weeks. (Although I still wonder if the 100 degree weather isn't a part of that).

Anyway, my CYA came up to 70 after a week on the auto-feeder, so I put in a gallon of 6% this morning to bring me up to FC of 8. We'll see how much I'm having to add each day to keep it there (hopefully not a gallon / day!).