Shocking An Indoor Pool

by Dawn
(Saskatchewan, Canada)

What would happen if a person would accidentally forget to open up the filtration system befor they shock the indoor pool?

Can you please respond right away otherwise I'll get no sleep tonight from worrying about what could happen, a person could be in a lot of trouble.

Thank you.

Thanks for the question Dawn

When you say to open up the filtration system, do you mean to have the system on "FILTER" as you would for a normal cycle? I will assume this is what you meant.

To do a proper shock, especially with an indoor pool, you need the system to be on "FILTER" and have the indoor air ventilation/exhaust going as well. By not having these on, the chlorine will just sit in one place, probably sink to the bottom, and not be circulated through the entire system. This includes the filters.

One full turnover of the water needs to happen for a proper shock. If it's a commercial pool, at least here in the states, the gallons per minute (GPM) needs to be around 280 GPM. For a home indoor pool, it's about 40 GPM. You probably use the metric system and liters, but it's still the same rate.

An example is this - You have a 25,000 gallon indoor home pool at 40 gallons per minute. That's 2400 gallon per hour. 40 X 60 (hour). A full turnover would be about 11 hours. 2400 GPM X 11 hours = 26,400.

A commercial pool, say 100,000 gallons. 280 GPM X 60 minutes = 16,800 gallons per hour of water is being filtered. It would take around 6 hours for a full turnover of the water.

So the short of it is this - the filter needs to be for a proper shock and the indoor fresh air/ventilation/exhaust.

Hope this helps and have a great day.


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Chlorine Testing For Indoor Pool

by Jerry

When Alkalinity and PH are within normal range, and after adding 5# of shock, still not getting ANY reading on test kit.

Pool size is approx 20k gal. Indoor and maintained nearly daily. Been fighting this problem for more than 2 weeks.

What am I overlooking?

Thanks for the question Jerry

First I'd like to have a few more things:

- Your pH and alkalinity readings. A "normal range" can mean different things to different people.

- The kind of shock you're using. Is it a normal chlorine shock or is it Dichlor. This is a stabilized form of chlorine that adds stabilizer into the pool.

- Your test kit. Are you using test strips or a dropper test kit? If a dropper, what kind, the Reagent or OTO yellow kit?

- Do you use chlorine tabs or another kind of stabilizer? Some people use stabilizer in indoor pools. I'd like to have your stabilizer level as well.

Your problem with not having a reading could be a few things. First, if you' re using test strips, they might be old or not able to read the chlorine for some reason. I use and recommend a Taylor FAS-DPD K-2006 kit.

Pool Water Testing

Water Testing Kit

For a 20K gallon pool, if you put 5lbs. of shock in it, the chlorine could be as high as 15 - 20ppm. This is called a "bleach out" where the chlorine level is not being registered, especially if you're using strips. Most strips can only measure chlorine levels up to 8 - 10ppm. If this is the case, you can take a sample to a local pool store to analysis. They should use the FAS test kit.

I would advise you to not shock the pool unless you test for chloramines. This is the organic matter in the pool and can easily be tested using the FAS kit. Shocking is meant to kill the bacteria in the pool, but only if it's not being properly treated.

If you maintain a pool, there really is no reason to shock because the chlorine will be doing its job in killing the organic matter and bacteria.

Here are some posts about that:

Do You Really Need All These Chemicals For A Pool Or Are They Just Trying To Get Your Money?

Shock The Pool & Chlorine Tabs

Only shock when you need it, not because it's Saturday. Here's my page on indoor pools:

Indoor Swimming Pools

This could be a very simple issue to resolve. Just get me the extra info. that I mentioned above and we'll get it straight for you.


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