I'm trying to determine the least amount of chemicals that I can use while still keeping my spa water is good condition. I'm using an ozonator and dichlor. My spa is 350 gallons.

I have a few questions;

Do I need to add any dichlor after a fresh fill and water balancing or can it wait until after the first use? If I do need to add it at startup, how much dichlor should I add? I use treated city water.

How much dichlor should I add after each use?

How much dichlor should I use when I shock?

How often should I shock?

Any help is greatly appreciated.

You need to maintain a residual. There's no set amount that you will use after each use.

If your aim is to use less chemicals, dichlor is a bad option for constant use. Since it adds stabilizer to the water the free chlorine residual you need to maintain will constantly rise. Consider using liquid bleach or bromine tabs for everyday sanitation.

You'll also need a good test kit for whichever sanitizer you choose (chlorine/bromine). Once you can accurately measure the sanitizer level (and CYA level if you use dichlor) you can figure out what your free chlorine/bromine level needs to be and how much of whatever chemical you're using to add.

Spishex - Thanks for the reply.

By liquid bleach, do you mean laundry bleach, not ultra or scented, just plain old liquid bleach? If yes, what would be a starting point for a 350 gallon tub? one cup, one tblsp...

I'll be picking up a good test kit very soon. Are there any you recommend?

I see you are local to me, do you have a store in the area?

Oh, look at that! I'm service only, but I contract for a few stores in the area. For dosing a good tool is The Pool Calculator. And yes, that's just plain unscented bleach. No additional ingredients. But do consider using bromine since you can just use a floater that way and you won't spend so much time adding chemicals.

The test kit will depend on whether you use bromine or chlorine. If you use chlorine you'll want to use an FAS-DPD kit (either Taylor K2006 or TF100). The TF100 has the added benefit of being supported by the manufacturer and users at troublefreepool.com. The chemistry is the same.

If you decide to use bromine you'll need the Taylor K-2106.

Hi,

Bleach? I wouldn't put bleach in my hot tub!

Bromine is what most use in a floater, and will use dichlor additionaly when having high bather loads(floater can't dispence enough)
With Bromine, you will use 1ppm/per person/every 15 min.

For testing, drop kits are most accurate, test strips will give you a general idea.

Your dealer should have a water testing station to give you the most accurate reading.
If they don't, try to locate one that does.
On every fresh fill, you should get it tested, as the quality of city water can fluctuate quite dramaticaly

Cheers

When it comes to sanitizer levels, a fas/dpd kit will give more accurate readings than a typical drop kit or most store testing stations which also use liquid/tablet dpd or other colorimetric tests since titration rules out any guess work. While a titration test is still part of a 'drop' kit, so is an OTO test which is ok for rough ideas but horrible for accuracy, so be careful what you pick up.

There are only a few things a store will be able to test for more economically than you can: copper, iron, sometimes manganese, and total dissolved solids. The treatment for all three metals is the same, and once you know you have them you can treat them as a matter of maintenance and should not require further testing. TDS is only marginally useful, and if you're adding salt to the system through bleach or for a generator it is basically useless.

Bleach is fine to use in a pool or spa if you're going to use all chlorine. The amount of CYA added by tablets or dichlor is too high for constant use, ditto with calcium in cal-hypo. The only problem is that it's labor intensive. In the end, they all give you Hypochlorous Acid.

I use bromine tablets in a floater, monopersulfate for shock, and liquid bleach on the rare occasion that I need to add more sanitizer quickly.

Nothing wrong with using good old chlorox bleach. Some of the "speciality" spa chemicals are nothing but sodium hypochlorite

aka beach with out the water added. The problem with bleach is it decomposed to sodium chloride aka salt

which a little is ok but after a while it becomes another problem to address.

Read the labels you'll be surprised what common chemicals the consumer is being grossly over charged for.

Di chlor is also fine, but use carefully and allowit to disipate, unless you want to brighten the bathing suite a bit.