Will chlorine levels drop from 5ppm to 0ppm in day

[squale]

after each use of my spa I put in about 2 teaspoons of dichlor.. this usually brings the chlorine levels up to about 4-5ppm.  Then about 12 hours later with the cover on and nobody using the tub.. when I check the water my chlorine levels are usually only at 0-1ppm.  So is it normal for chlorine levels to just drop down on their own without using the tub?  and how quickly is it normal for them to drop?  

I am having a really hard time trying to keep the tub at 3ppm of chlorine at all times.. I can bring the level up really fast but then it just drops quickly too..

[Vinny]

"Officially" there should be a residue all the time but honestly I doubt any of us keeps a residue. If you find after 12 hours you normally have some chlorine then you are OK. If you use the tub the next day then you start the cycle over again. This is where the use of bromine comes in ... it can maintain a constant residue or at least with a feeder.

If you skip a day you still may be OK but if you skip 2 then add chlorine.

Have you shocked your tub with chlorine? Every so often it is a good idea to add more chlorine than normal just in case the bacteria didn't all get killed. The extra should do the job.

How long does chlorine last ... I truely believe that it's different for everybody even if we owned the same tub and set it at the same temp. I have gone 24 hours and had a residue left. But if you find that your chlorine levels go down extremely quickly then hit it really hard with chlorine (10 PPM or more) this is an indication that you have something using up the chlorine. BTW as you use chlorine (dichlor) you are building up stabilizer and this causes the chlorine to become less effective and you might need a little more to do the same job.

[squale]

well I usually shock once a week with 2 ounces of MPS... what is better for shocking.. MPS or Dichlor?

[Vinny]

MPS is great for oxidizing but doen't have the extra killing power of more free chlorine.

The rule of thumb is to shock with 10x the combined chlorine amount with free chlorine (ex: 0.5 CC = 5 FC, 1.0 CC = 10 FC ...).

Using MPS is good as it really burns up contaminents but it is a good idea to use chlorine as a shock every so often just to make sure any resistant to normal dosing bacteria gets killed.

[Hillbilly Hot Tub]

Your chlorine level dropping that quickly means that the chlorine is working on something in the water, getting used up. Increase you dose of chlorine untill you oxidize the contaniments and start maintaing a chlronie reading. Metals in the water will chew up chlorine as well as risdual soaps from swimsuits ect. Have you tried a clarifier and then cleaning your filters super well to remove any contaniments/waste from the tub? I see in other posts you have problems with smells ect. Also a sign of contaniments. Strong chlorine smell means not enough chlorine (usually) as strange as it sounds. It is working to hard. Mildew smells and body oder smells mean not enough chlorine, stuff is growing. Even if you are clean when using the tub, each person sweats about a pint per spa use...this will cause BO smell if there is not enough sanitizer to kill the microorganisms. As stated in another post, PH is important for keeping the chlorine working right as are the CYA levels.