What is the best HOCL (as ppm CL2) number to aim for

[chem geek]

Your experience lends further support to the theory that SWG pools can have a lower FC target because free-floating green algae gets super-chlorinated in the SWG cell. Yellow/mustard algae tends to settle and not free-float so won't get circulated as readily. So that would make the manual and SWG chlorine levels similar for that algae, namely an FC that is 15% of the CYA level.

For most SWG pools it is better to use a higher CYA level of 60-80 ppm since that will have the chlorine last longer (even at higher FC levels) and let you turn down your SWG output (since less absolute FC loss per day) which helps reduce the rate of pH rise. However, in your situation, that would require (in theory) an FC of 9-12 ppm to keep the mustard/yellow algae from growing.

This is one of those rare times where one of two things can be done. One is to super-shock the pool at 60% of the CYA level so in your case probably 25 ppm FC to be conservative and hold it there for several days and put everything and anything into the pool that might be harboring the algae, such as poles, etc. Even remove the lights from their niche to expose chlorine behind them. If you completely kill off the mustard/yellow algae, then it may not come back even at more normal FC levels.

The other option is to have your phosphate level checked and use a phosphate remover if its high (or even if its not, in this case). This is rarely suggested but it is another option to allow you to get to a lower sustained FC level. It's up to you what to do.

Richard

[smallpooldad]

chem geek,

Thank you for your informative reply.

My question is (I am a little confused) if I just leave it the way it is as there is no algae visibly present and the unit is running at the mid-power setting of 2, which was recommended by the senior tech at Pool Pilot, would that not be the solution? Only issue is it does have to run nearly the full three and half hours to reach 700 ORP.

As you stated raising the cYA seems to me that I would need too much chlorine, which would require running the pool pump for a long period.

But the number I gave 5.5 FC appears to be ok from a health and swimming point of view, or is that not correct?.

I'm not sure where the yellow stuff comes from but where we live at a 1000 ft the trade winds roll over the mountain daily at about 16 mph to 26 mph on average blowing fine stuff (particles) constantly into the pool. So while we may cure it temporarily in all probabilty it will return just as fast. Therefore my feeling is to leave it as is, or do you think this is not wise? I will certainly give the phosphate suggestion a go and let you know if that has any effect I could become the pool stores only Diamond Card client if it does at least until I have to eat and stop buying phosphate remover.

The pool is pretty much 4 ft 6 in deep all the way round with steps into it, that is why I thought the UV may play a roll.

Finally what do you think is KWH use is of the SWG. I noticed in another thread on cost of chlorine nobody seemed to factor this in, or I could be mistaken.

As always thank you once again for all your great help. In this case I think I am between a rock and a hard stone.

[smallpooldad]

It might be that the winds whip up a higher "Organic Load".

I found this article interesting; any thoughts?

http://www.water.siemens.com/SiteCol...20Chlorine.pdf

[chem geek]

Many times people think they have yellow/mustard algae when they really have pollen. The main difference between the two is that the yellow/mustard algae will tend to stay on the shady side of the pool while the pollen will settle wherever circulation takes it and usually right on the bottom. Yes, pollen will create an extra organic load and therefore a chlorine demand. A skimmer sock is often the best way to remove the pollen as it tends to stay on the surface for a while so can get into the skimmer before it gets water logged and drops.

If you are able to get a sample of these yellow spots (carefully taking a turkey baster or something like that to suck some up), then if you look under a microscope you can tell the difference more readily. Pollen is round or spiky and solid-looking. Algae is more translucent and usually oblong.

You may be correct that you have pollen instead of yellow/mustard algae. That is usually the case. However, higher chlorine levels won't keep away pollen, but it will tend to break it down faster.

Richard

[smallpooldad]

chem geek,

You are correct it is pollen, so now I keep the cover on and that seems to reduce the problem; taking it off for 2 hours a day to vent the pool.

Thank you for your help.