community pool just does not get clear!

40,000 gal. inground pool, pH 7.4, FC 10, CC 0.5, TA 100, CYA 30. Tests done with Taylor K-2006.
We tried to turn our green swamp into a clear pool without emptying it. This might have been a bad idea. Now the pool is blue but not clear. We can't see the bottom of 5 ft. We also had a lot of white foam on the pool when we started this after backwashing. Now the foam has stopped. Do we have to let all the water out or just some, or is there anything else we can do to get it clear and sparkling? Please help!

Filtration is the way to clear the cloud after killing the algae. Please tell us more about your filter and pump and what chemicals you've used so far.

Please list:

1. Your filter and pump make / model. (Pump model is usually on the WET end, not on the electric motor. Motor will give you HP, amps, and SF (service factor), but not pump info.)

2. ALL the chemicals you've used since you started opening, in approximate quantities.

3. Approximate dates (open, physical cleaning done, chems added. etc.)


. . . I've got to run. I'll add to this later this evening. Meanwhile, if you have a sand filter, it would be a good idea to purchase a bag of DE filter powder. The DE will BOTH enable you to 'test' your filter, AND help you clear up any fine particles in the water.

We have a Pentair Challenger 5 Hp pump and two 36" sand filters. I have so far added 4 times 11 jugs (96 fl oz) 6% bleach and 1 time 14 jugs (96 fl oz) of bleach. I waited a day or two in between putting in the bleach. I also used approx. 2 lbs of Super Chlo Calcium Hypochlorite (67%) twice when I had no bleach at hand. Brushed a lot and fished out a lot and backwashed 6 or 7 times. Put in approx. 25 lbs of soda bicarb to raise the TA and one jug muratic acid to get the pH from purple down to red.

Presumably, that's a very big pool: how big?

Meanwhile, you'll need to get a 25# bag of DE powder:

Diatomaceous Earth (DE) Pool Filter Powder 25 LBS. @ Amazon.

You may be able to get it for less, locally at Home Depot, Lowes or a pool store. You'll need it BOTH to test your filter, and to help cleaning up the water.

And, you'll also need a K2006 test kit - links below in my signature.

Re-reading this, I'm guessing you have a commercial pool? If so, you need to get the K2006C (2 oz size) PLUS (2) K1000 kits. Also, you need to tell me what your daily bather load is, and whether the pool is outdoors or inside.

The pool belongs to a home owners association and I am a home owner who takes care of it. The pool is L-shaped and holds approx. 38,000 to 40,000 gal. of water. It is not open right now. We just bought 25 pounds of DE. I have never worked with DE but assume you put it in the sand filters. Correct? If yes - we will put it in this afternoon, because I need some help doing this.

Do NOT put it directly into the filters!

Instead, put about 2 quarts -- 1/2 gallon -- of DE into a skimmer while the pump is ON. Then, go watch the return jet closest to the filters. If DE shoots back into the pool, your filters need service. If not, the DE will help filter fine particles, but will likely cause the pump pressure to rise much more quickly, so you may need to backwash in much less time than usual.

You'll still need the kits . . .

When you wrote that the "pool just does not get clear", did you mean just this spring, or normally?

Also, what chemicals and processes have you used trying to clear the pool this spring?

I ment only this spring it does not get clear. In the 20 years that I lived here they always drained the pool completly and started with fresh city water. This year we wanted to see if we can turn it from swamp to clear for the first time. After I have spent endless hours working on this (approx. 2 per day) I will not do it this way ever again. The electricity to run the pool 24/7 cost the same as new clean water. All the chemicals I have used so far are mentioned in #4! No I am starting with the DE.

Cleaning up swamps can be uneconomical. In years past, when I serviced multiple very large commercial pools, I'd sometimes have to clean a swamp. Usually, I'd dump 3 - 4 gallons of 15% industrial bleach for every 10,000 gallons of pool water (30 - 50 ppm). It would turn gray within an hour and cloudy blue within a day.

But I was buying fresh bleach at ~$0.50/gallon. That was MUCH cheaper than any form of chlorine you or most pool owners can buy.

Test with the DE; give me what test results you've got; tell me what color the pool is; and ORDER the K2006!

One really important point: killing algae is much easier with one very large dose of chlorine, than with 4 smaller doses. The small doses allow the algae to recover, and tend to be wasted.

You should be able to keep it clear over the winter. I always keep my pool open as long as possible so I can keep adding chlorine until the nights start having below freezing temps. Then, I open it early in the spring. My water is always clear. I do not cover my pool in the winter and do have a little dirt in the bottom in the spring, but that is easily vacuumed up.

Last night we put the DE into the skimmer, but we can't see the returns at the bottom because of the cloudy water. Nothing came to the top - does that mean the filters are OK? We had to backwash within 1 hour of adding the DE. The pool does not look any clearer today. Does the DE go away with backwashing? Should we keep doing this again?

If you can't see the water stream from the returns . . . it doesn't tell you anything. The DE is either on top of the sand in the filter, and will be backwashed out OR it's sitting on the bottom of the pool along with the dead algae.

*If* the DE is on the filter, you should see filter pressures rise much more quickly than normal. If this is not happening, I'd recommend opening one of the filters and checking sand levels.

Something just occurred to me -- if someone has backwashed the filters one at a time, instead of doing both simultaneously, odds are you've blown much of the sand out of the filter. I'm guessing the flow curve below shows your pump on the "F" curve. If so, that pump will deliver WAY too much water, during backwash, for a single filter. Maximum backwash flow on a TR-140 is about 110 GPM. That pump can deliver 2x that rate of flow.

If the standard practice at your pool has not been to backwash both pumps simultaneously, you'll need to (a) replace the missing sand and (b) develop a process that will ALWAYS be followed during backwash, in order to prevent excessive backwash rates.

http://www.pentairpool.com/images/pr...wCurve_new.jpg

Sorry it took so long to write back. We used to backwash both at the same time and then someone told us this was wrong and we backwashed one filter at a time. Tried to get into the sand filters and broke the handles of the tool.
Our pool is 34 years old - maybe the plastic tool got brittle. Got a new handle and broke it again. Last night we finally managed to open the filter tops and a lot of sand is missing. We added the sand and it starts to look better already. Thanks a lot for all your help. I hope it is looking clear tomorrow!

Glad you worked it out!