Blue Oily Substance On My Filter

by Vojislav
(Broadview Heights, Ohio)

After closing the pool and taking out the filter for winter storage, I noticed a blue film on the filter. In touching it, it appeared to feel like an oily blue paint, but it was wet. What in the world is this, and I threw the filter away.

Thanks for the question. It's really hard to say without the chemical numbers or looking at the cartridge. I can tell you that it is abnormal, but most of the time what is found in the filter has to be introduced into the water by some outside source. It could be a different chemical, or some kind of chemical reaction, or someone put a product in the pool without your knowledge. It might be paint (if your pool is painted) or something else. With the limited amount of information I have, trying to find the cause is very difficult.

A blue oily substance in a cartridge filter is uncommon so we would need to conduct a process of elimination to find the cause.

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I have a 50 year old in ground 8" thick gunite pool with a 3/4" white plaster coating (see picture). The pool is 35'x17.5', 24,000 gallons, rectangular and leaks less that 1/8" per day.

About 5 years ago I drained it and sanded the sides and bottom to (1) remove blue copper coating on plaster and (2) smoothe the bottom which was like coarse grit sand paper. About 3 years ago I converted from the original sand filter to a cartridge filter.

When I clean the cartridge filter I get white sand down to white powder (white cement). See picture. This may have been going on for years but with sand filter you don't know what you are flushing away. The pool chemistry is always good, i.e. PH about 7.2 to 7.6 - not acidic. I clean the pool with a Kreepy Krauly.

I have swept up the white sand/powder and estimate I am loosing about 5-50 cubic inches per year. The nominal 3/4" white plaster has a volume of 99,500 cubic inches. So at this rate at 50 cubic inches/year I will only loose 2%-3% of the white plaster coating. And since it still doesn't leak I guess I am worrying about nothing.

But if anyone has had a similar experience with their in ground plaster pool and their cartridge filter I would very much appreciate any thoughts.

Thanks for the question Jerry

There could be one or a combination of things to consider. Given the information I have I can go over what it could be.

Unbalanced water can cause the plaster to degrade. Even though the chemicals may be correct right now, there could have been a time when they weren't. High acid use can also aggravate the plaster. Using too much acid to lower the pH and TA can degrade the binding between the plaster and pool shell. High pH can be caused by high pH fill water, overuse of sodium bicarb or soda ash, or overuse and shocking with calcium hypochlorite. Cal hypo can also raise the CH.

A rough surface can be due to calcium deposits or high calcium fill water.

Spalling is a peeling of a layer of plaster. This can happen in the shallow end and on the steps. It can be caused by the troweling of the surface when the plaster paste is still wet but the concrete is dry.

Delamination is the separation of the new plaster from the concrete or underlying surface. It's normally caused by a surface that was improperly prepared to create a good surface for the new plaster. It can take several months or possibly several years for this to work through the process.

I hope this has answered your question to your satisfaction.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Cartridge Filter" category.

Check back to this post for updates or answers.

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Have a great Summer.


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Cartridge Filter Keeps Getting Dirty

by Sandra
(Cincinnati, Ohio)

I am a canine hydrotherapist and have been operational for 6 years I have had 3 different filtration systems, DE, Sand and Cartridge Filter. In September, I installed the largest cartridge filter system that Hayward (C2002) makes. A new filter cartridge is only keeping the water clean for about a month. I have been cleaning the filters with TSP and Muratic Acid but the reused filter is dirty after 2 weeks of use.

This is very labor intensive but the filters are too expensive to discard after one use ($150). I have a Florida North 8 x 20 x 4 swim spa. Water temp 90-94 I use chlorine and a UV light. Currently I am seeing 30-35 dogs each week. This is an indoor pool. I would appreciate any help you could give me.

Hi Sandra. There are a couple ways you can go with your issue. First is to get a pair of knee high panty hose and wrap it around the skimmer basket. It's another layer of filtration before the dog hair and oils get to the cartridge filter. Only use one at a time. And you MUST be diligent in cleaning it. It can clog quickly and will reduce water flow to the pump motor. This is the less expensive.

Next is to use a skimmer sock. These can be found online, perhaps Walmart, or your local pool supply store. They act in the same manner as the panty hose.


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swimming pool care, basic pool care, above ground pool maintenance, inground, salt water

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