Chlorine-less Shock

[mphare]

I have an Aquarite SWG. The guy at the pool store (I know, pool store) recommended I use a non-Chlorine shock rather than the standard chlorine shock.

I've never heard of non-Chlorine shock. Anyone have any history with this stuff? Is it really desirable over standard shock?

[chem geek]

Mike,

The most common non-chlorine shock is potassium monopersulfate (KMPS). It is best used as a maintenance product once every week or every two weeks as it is much better at oxidizing organics BEFORE chlorine combines with them. It is not very good at breaking down combined chlorine (CC) that has already been formed. It is not cheap.

However, there is probably no need to shock your pool at all. Most outdoor pools exposed to sunlight do not build up combined chlorine while outdoor pools with SWG almost always have zero combined chlorine, so no need to shock them. The SWG superchlorinates a portion of the water that passes through the cell and this seems to keep the combined chlorine near zero.

Do you have a good chlorine test kit (e.g. Taylor K-2006) that measured a combined chlorine amount and is that why you believe you need to shock, or did the pool store just assume you should be shocking regularly? If the latter, they are probably wrong and you shouldn't need to shock.

Richard

[mphare]

Thanks,

I have a Taylor K-2005 which can test for free and total chlorine, so I can calculate combined. And you are right, I've never really had the need to shock, except during the late winter. The days get warm enough to cause problems, but the water doesn't get warm enough to generate chlorine. I usually end up with a bloom every year about the end of January to mid-February.

So I will shock every so often during this time to keep the water clear.

Is there an advantage to using the non-chlorine shock? Should I be using a non-chlorine shock? or is it just person preference?

[chem geek]

Mike,

OK, now I understand what you meant by shocking the pool. When the SWG is shut down due to colder temperatures, all you need to do is add chlorine (chlorinating liquid or bleach) to your pool. You don't need to shock it, but you can add more than you usually do if you don't want to add it as frequently. The chlorine will keep it from developing algae. That's what I do and it works well.

Some people just let the pool go over the winter and then clear the algae upon opening while others add chlorine during the winter to prevent the algae. It's really up to you as both options work. It should be relatively easy to add chlorine during the winter since the chlorine usage is much less due to the colder temperatures (so the algae doesn't grow as fast and doesn't consume as much chlorine, plus the sun isn't as strong).

The use of non-chlorine shock with no chlorine in the water will NOT prevent algae. You have to have chlorine in the water to prevent algae (or an algaecide, but chlorine is cheaper).

Richard

[CarlD]

There are lots of ways the pool industry tries to move money from your bank account to theirs.

I'm a believer that non-chlorine shocks are one of them, as are most algaecides.

In the fall before closing, I boost my FC to ensure I have no CC, then add a quart of polyquat algaecide (the only one we recommend here). I wait 48 hours then boost my FC up to the shock level for my CYA (stabilizer) level and close.

All I do all winter is syphon out some water if it gets too high. I've yet to have algae in the spring...so watch, this year will be the first time ...but not yet. I just checked yesterday and the water was clear, despite having a surprisingly mild fall and winter.

[mphare]

Thanks.
I had a feeling I was getting a 'shock treatment' from the pool store guy.
I just wanted to be sure.

I'll remember that next year when I close for the winter.
I'll just keep some chlorine in the pool (I'd rather not have to clear an algea problem if I don't have too.)

Thanks again!