Is shocking necessary?

[cscannon]

Do you shock only when you have combined chlorine or do you shock weekly like the pool store people suggest?

This is the first summer that I have been using pool forum and I have been running my cya at 60-80 and FC about 5-6 as per the "best guess chart". I used to run FC at 2-3 and frequently had combined chlorine which I would shock but since increasing my targeted FC I haven't had any combined cholorine.

30,000 gal SWG gunnite pool.

Steve

[chem geek]

Steve,

You do not need to shock unless you have measured combined chlorine or unless you are battling algae (or sometimes if your pool is cloudy, though other factors can cause this that chlorine won't fix). You can always shock after a heavy bather load or a heavy rain if you wish, but it isn't necessary. Also, the combined chlorine will get reduced somewhat slowly so even if you measure combined chlorine at one point in time (immediately after swimming, for example), it could go down later (assuming you have chlorine in your pool) especially after exposure to sunlight.

The pool store is wrong that you need to shock weekly. See this thread for a small sampling of how often users of this forum shock their pools. It seems to be about 0-4 times per season, with most only shocking once or twice per season.

Richard

[cscannon]

I love Pool Forum! The kids who work at the pool store don't even know what combined chlorine is. It makes me wonder how much bad advice I have received during my life from people trying to sell me stuff.

Thanks,

Steve

[chemistrydropout]

I am a complete newbie to the pool business. First year with a pool. I have only shocked 3 times this summer. During heavy rain events I have noticed that my pool liner will be slightly less "squeaky clean" than it normally stays. I have never had any combined chlorine reading above .5 but my intuition tells me that when something is going on in the pool like this I should shock to make sure. It only cost about $10 and the piece of mind is worth it to me. Now this goes against what some people believe here and with more experience I might change my protocol. It just gives me piece of mind. I also have a continuous heavy swimmer load and lots of debris gets in my pool during thunderstorms. FWIW

[chem geek]

Now this goes against what some people believe here and with more experience I might change my protocol. It just gives me piece of mind. I also have a continuous heavy swimmer load and lots of debris gets in my pool during thunderstorms. FWIW

Unless you keep your chlorine levels on the high side, or even higher, in Ben's Best Guess CYA chart then your high bather load and debris can certainly consume lots of chlorine and generate a lot of chloramines that take time to break down. With such an overload situation, you can either shock periodically as you are doing or you can operate at higher chlorine levels all the time. Sliminess in the pool is usually more related to algae starting to form than to chloramines (and you said you had CC measure at 0 and probably don't smell chloramines either). So perhaps your chlorine level is on the low side given your particular pool situation. Just a thought. If you post your numbers, especially FC, CYA, pH, then perhaps this will give us some useful info for a "heavy bather load and debris" situation.

Richard

[chemistrydropout]

Fc 3
cc < .5
Tc 3
alk 80
cya 30
ph 7.5
ch 120
H2o temp 87

Richard, I did not necessarily say that the liner was slimey. I just have a feel for how nice and sqeaky clean I like the liner to be and after heavy thunderstorms I have noticed that the liner does not feel just right sometimes. Funny thing is though last week I was having trouble getting it just right and I had a group of 5 people swim for about three hours and it actually improved the situation. I am contributing this to the fact that 3 adults and 2-8 year old kids can move more water around than a 1 horsepower pump could in a week or so. By the way I keep a close eye on the water conditions. Test daily and when I think things are going south I like to test morning and evening.