DE in pool - not the simple answer

[PME]

Hello,

I have DE in my pool and I can't find the reason why. I have been taking care of my pool for 16 years. Recently, I had some DE in the pool and I was sure there was a hole in a grid. I had replaced them the last time I cleaned the filter. So, I opened it up and they all look just like new. After cleaning the filter 3 times, each time thinking that I missed something, I still have the same problem. Then, grasping at straws I thought maybe something was going on in the backwash valve and because the filter was old (Purex SMBW 2060) and parts are getting scarce, I bought a new Pentair SMBW4060 and I have the same problem. It takes a couple of days but I get a coating of DE on the steps. I am using the same quantity of DE as I have used for 16 years. Does anyone have any ideas? I would really appreciate anyone who may have had this experience to give me some help.

Thank you

 

[JohnT]

Are you having any problems with air in the pump basket? Air in the filter is compressed by the pump, and when the pump shuts off the air can expand and burp DE into the pool via the skimmer.

 

[PME]

No, that seems to be ok. And, the DE is also in the raised spa which shares the same filtration.

Thanks.

 

[UnderWaterVanya]

Could you put socks on the returns and verify that the DE is coming in from the returns?

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[PME]

I would have a hard time doing that - I have 6 returns, 3 high and 3 low. I use an ozonator and the low returns were installed to spread the ozone.

 

[carolina pool]

It might be a crack in the manifold, which could easily be overlooked, or the air relief screen

 

[PME]

The manifold looked good but I replaced it anyway. And, I also replaced the relief screen. And, of course, when I got the new filter, it came with these items. Should I take the relief system out and plug the hole?

 

[zea3]

Hi, I have a couple of questions for you. What is the pressure on the filter when the pump is running? Have you recently replaced your pump? What is the horsepower of your current pump? Could you post a complete set of test results? We may be looking at a water quality issue instead of a filter problem. Also, what brand and type of chemicals are you using to maintain your pool?

 

[PME]

The pressure is 16 psi. I have not replaced the pump - believe it or not, it is the same Purex WF-4, 1 hp pump that I installed 16 years ago. I have an ozonator and I don't use any routine chemicals. I use calcium hypochlorite to shock and kill the algae once a week in the summer months. I don't have any conditioner in the water because I don't want the chlorine to stay in the water. Chlorine is 0, the ph is high at 8.0, alkalinity is 160, I don't have what I need to test the hardness but I would guess it is high because the water hasn't been changed for 8 - 10 years.

Thank you for your effort.

 

[JasonLion]

That could be a damaged, or misplaced, o-ring inside the filter assembly.

 

[Bama Rambler]

Are you sure what you're seeing is DE? What does it feel like if you squeeze it between your fingers?

 

[PME]

I don't think there are any o-rings in the filter except the ones at the manifold and of the course the backwash valve. I have changed the o-rings at the manifold and replaced the entire filter (including the backwash valve) and I still have the same problem.

Am I sure that it is DE? It certainly looks like it. It's a very thin layer that gathers in some edges on the steps. It is in the spa and on the steps in the pool. I just went out and gathered a pinch in my fingers - it feels like DE also. However, I am not an expert. I have only taken care if this pool all these years. I haven't been exposed to any other pools.

I really appreciate your time. Thank you!

 

[duraleigh]

It's a very thin layer that gathers in some edges on the steps. It is in the spa and on the steps in the pool.

Hmmm. It seems that DE from the returns would gather mostly on the pool floor underneath the returns.

With the pump running, that may not be the case, however.

I think it is essential to correctly identify it first and I am not a DE expert so perhaps some others will chime in with an easy way to identify it.

 

[Bama Rambler]

What's strange is that it didn't go away even after you changed the filter.
Do you have a slide valve or a multiport valve?
Did you change it when you changed the filter?

 

[PME]

If you are talking about the backwash valve, I think it would be a multiport valve. It is part of the filter assembly that I changed out (Pentair SMBW 4060). So, it is new.

 

[Bama Rambler]

I see that it has the rotary valve under the bottom. Not exactly a multiport but it's a moot point as it came with the filter so there's still a mystery as to what the stuff is and where it's coming from.

Tie a sock or stocking over a return or two and let it run. See if any DE (or whatever) gets caught in the sock/stocking. That should tell you if it's coming from the filter. Also put a skimmer sock in the skimmer(s) and see if they catch anything.

 

[PME]

Ok, I'll try that. I will put them on right now. I have to leave for a while. I'll respond later with the results. Thanks.

 

[zea3]

The pressure is 16 psi. I have not replaced the pump - believe it or not, it is the same Purex WF-4, 1 hp pump that I installed 16 years ago. I have an ozonator and I don't use any routine chemicals. I use calcium hypochlorite to shock and kill the algae once a week in the summer months. I don't have any conditioner in the water because I don't want the chlorine to stay in the water. Chlorine is 0, the ph is high at 8.0, alkalinity is 160, I don't have what I need to test the hardness but I would guess it is high because the water hasn't been changed for 8 - 10 years.

Thank you for your effort.

I am thinking you may have an algae bloom that is trying to take hold. The best way to confirm this would be to wait until the sun goes down and administer a shock level of chlorine to your pool, let it circulate for 1/2 hour and test the chlorine level. Test the chlorine level again in the morning before the sun is on the pool. If it has dropped by more that 1ppm then you need to complete the shock process on your pool.

How often are you vacuuming the pool? Another way to check if it is algae or not is to vacuum the pool clear of all debris, then turn the pump off 12-24 hours. If the debris has accumulated on the pool floor again, it is probably alga.

 

[PME]

I am open to any ideas but as to the algae bloom, this problem has been going on for 4-5 months. I have vacuumed the pool several times (during that period) after each time that I did something with the filter. Each time, after a couple of days, I have this white powder gathering on the steps of the pool and spa. I don't see it on the floor of the pool because the Polaris cleaner stirs it up. I am pretty sure that I have shocked the pool during this time but I have tried so many things, I am not sure. However, do you still think this could be an algae problem since it has been going on for so long?

 

[zea3]

Not being able to put eyes on the pool myself it is hard to say, but I do think it is a possibility. If you have read through our Pool School then you know we advocate maintaining a residual chlorine level in ratio to the CYA level. This keeps a level of chlorine sufficient to prevent algae from taking hold and kills off the vast majority of organisms that can cause disease. You say this problem has been going on the last 4-5 months. Algae grows more slowly when the water is cold. You don't say where the pool is located, but in most parts of the US the swim season is over by October. You may have been adding enough chlorine to keep the algae levels low, but not enough to kill it completely. Dead algae leaves a debris similar in appearance to DE. If it is an algae problem you will see the pool get significantly worse as the water warms. If it is a filter problem you will collect DE in the sock attached to the return.