Why won't my pool get clean?

[mohawk]

I've been thinking - if I add polyquat to the pool before vacuuming and the brown goes away, then I should assume it was algae-right? Then vacuum afterwards.

[chem geek]

To all posting with pool issues (rilesworld, mohawk): please post a complete set of numbers including FC, CC, pH, TA, CH, CYA. Otherwise we are really shooting in the dark here. The CYA level is very important to know as that will tell us how much chlorine is needed to battle this algae.

As for PolyQuat, it is generally not as effective at killing larger amounts of algae as it is for preventing algae from taking hold. This may be from this chemical polymer being easy to clump free-floating algae particles together and to block their ion channels, but that PolyQuat may be unable to penetrate below the surface layer of a biofilm of existing algae.

Richard

[tphaggerty]

I have had the slickness with my vinyl pool in the past. From my experience, you don't always need to "shock" (or super-chlorinate) to get rid of it, but you do need to BRUSH. Someone above posted that they get this in the less well circulated areas of the pool, and I think that is a good clue.

If you maintain your CL levels (meaning it is pretty steady, not dipping to 0, then back up), you can normally get rid of any slimy or slick feel by brushing the walls AND floor. If the feeling returns, you may need to shock and/or increase your normal CL levels a touch.

Richard has posted many times about CL not being as effective on bio-films (until they are removed) and I think this is a thin bio-film of algae. Once it is scrubbed/brushed a bit, the CL can get right to the vinyl and should keep it away at your normal levels.

[rilesworld]

My numbers were as follows before I shocked:

FC - 4
CC - 0
Ph - 7.5
CYA - 40
TA - 90
CH - 190 (not sure about this one, but I vinyl so I don't test it often)

I went ahead and shock to 23 ppm just in case I was battling the Yellow/Mustard algae that Matt4x4 refers to.

My Ph did go up quite a bit with the shock is that normal? It reads about 7.8-7.9 right now.

I brushed and added some DE to my sand filter. I already seems to have helped. Although I won't really know whether it was shocking or the DE that solved my problem. I guess I don't really care at that point.

What is a safe chlorine level to swim at?

Thanks,

Riles

[chem geek]

Yes it is normal for the pH to go up when adding chloriniating liquid or bleach. As the chlorine gets consumed or breaks down from sunlight, the pH will drop back down.

With your CYA level, wait for the FC level to drop below 10 ppm though technically even 23 ppm FC with 40 ppm CYA is equivalent to only 1.4 ppm FC with no CYA (i.e. typical of what may be found in indoor pools that don't have CYA).

Richard

[mohawk]

Here are my numbers:
PH-7.5
FC-5.0
CC-0
ALK-220
CYA-Not on 30 yet.
I just added the 3rd 1.5 lb container on CYA into the pool and the return jet is bubbling on top for the alkaline.

[chem geek]

mohawk,

Just a reminder that if you want to lower your TA you need to lower your pH. Aerating at higher pH is not nearly as effective. See Lowering Your Alkalinity for more details on the correct procedure.

One thing you can do is to take some of this "brown" stuff with pool water and put it into a bucket that you keep in the sun (which will get rid of the chlorine eventually). When the chlorine is gone from the bucket (i.e. FC measures 0), cover the bucket with cheesecloth (possibly folded over to be doubled) or something that will let it breath and let some sun through, but will prevent any dirt from blowing in. Then see if the brown stuff grows in the bucket. If it does, then it's algae. If it doesn't, then it *may* be dirt or could be that we just aren't giving it an environment it likes enough.

If you have a microscope, you can fairly easily distinguish between algae, dirt and pollen.

If anyone has any ideas for a simple test to distinguish algae from dirt or pollen and doesn't involve a microscope, please chime in. It seems that this is a pretty common question to get answered, but unlike green algae that is easy enough to kill with chlorine, mustard/yellow algae is heartier so it's harder to tell from normal shock levels if it's algae or not.

Richard