Can't get rid of dead algae

[Cleggette]

Hello. Ok the diameter of the sand filter is 62" with a tape measure. I got home just in time to take the readings on the pool before it rained.

CL 7.5
Total chlorine 7.5
PH 8.0
Total alk 150
Calcium hardness 300
CYA 80
The pool is 90 degrees and the pump is running 24/7. Came home today and I can barely see the bottom of the pool.

I filled out the form with all my info about the pool and where I live but I can't find where to input my test results?

[PoolDoc]

So, an 18" sand filter => 27 GPM max flow rate for optimum filtration.

I looked up the Optiflo pumps -- they are 30 - 80 GPM pumps, which is WAY too much for that filter. I spent some time making up the image below.The original image is the Pentair data for the Optiflo pumps. I've overlaid some data for 18" SD40 and 21" SD60 Sand Dollar filters, which are similar to what you have. I got carried away with the curve, which shows the filters clean, and with a 6 psi (14' head) pressure increase as they get dirty. The pressure loss from the piping and valves is not included.





BUT . . . the curves from the pumps SHOULD cross the curves from the filter, somewhere, and they aren't even close.

What does that mean?

Most likely, instead of your filter having 27 GPM moving through it, it's probably got closer to 50 or 60 GPM! And at that flow rate, the dead algae is simply shoved right through the filter sand. It's the classic OVERSIZED pump, UNDERSIZED filter problem so common with AG pools.

And that problem typically shows up exactly like yours has.

The simplest solution is to install a ball valve between the pump and the filter, that allows you to throttle the flow back. Contrary to what most people think, this will actually REDUCE the amount of electricity your pump consumes.

The best solution is to replace your existing pump with this one:

Hayward SP15922S Power-Flo Matrix Above-Ground Pump 1HP 2-Speed @ Amazon

and then run on low speed except when vacuuming or backwashing.

OK. You can't get a pump immediately, so here are some immediate steps.

1. Do the DE test, to make sure that the sand hasn't been washed out of your pump during backwash. (This happens routinely in the BIG pump - little filter situation.)

2. Repair the filter (add sand?) as needed.

3. Install a ball valve between the pump and filter, and throttle the flow back so the filter shows 12 psi or less when clean.

[Cleggette]

Is the DE test the same thing as the cellulose fiber? We did that an nothing came back in the pool or no powder came in the little bubble so nothing is passing through the filter. I definitely cannot afford a new pump right now. How do I install the ball valve and is there no way to get this algae out of there without doing this? This is frustrating. I have had the pool less than a year.

[PoolDoc]

Not at all; use DE powder.

The ball valve has to be installed in the piping between your pump and your filter. Without seeing your piping, I can't tell you how to do it.

BUT, once your filter passes the DE test, you can continue to use DE, by adding say 2 cups after each backwash, as a filter aid. A small sand filter makes a tiny DE filter . . . but it will still filter dead algae better than than it will otherwise. But you'll probably have to backwash for 30 seconds or so, every day.

And yes, your problem is both extremely frustrating and very common. I remember many years ago, the first time I tried to clean up dead algae on an AG pool -- I couldn't figure out what was wrong. My experience had been with IG pools which tend to have bigger filters and not so big pumps, and I couldn't understand what was going wrong. I never did solve the problem, and I was very embarrassed about charging that customer for my time. But, 30 years ago, I didn't realize that the pool equipment companies were deliberately misrepresenting their products.

It's a common problem -- just this morning I posted on my Facebook page, a link about common deceptive advertising practices that affect ALL SORTS of industries.

I'm sorry there's nothing more I can do to help you. I *am* happy that we've been able to help a couple of guys, who are getting new pools right now, get BIG filters and little pumps, though. But most people don't come to the forum till AFTER they have problems.