Hot Tub Murky Water

by John

New hot tub owner: my water is getting cloudier by the day. FC 3.6 but won't hold for more than a few hours TC 4.8 CC 1.2 Ph 7.5 TH 126 Alk 80 CYA 66 Phosphorous 750 ppb The tub is a week old. I don't understand the CYA being so high with the water being only a week old. The hot tub store wants to sell me phosphorous reducer for 60 bucks but I'm not sure that's the trouble. I just can't seem to hold a chlorine residual, potentially due to high CYA.

I hate to change water after only a week. Also is it important to leave the cover off if shocking the tub so that impurities can off gas. I have not done so due to cold ambient temp. Any advice for a newbie? Any good reading/study materials to become a spa guru like you?

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Hi John. I want you get get going with your hot tub also. First is to stop listening to pool store employees about water maintenance. You'll end up spending $100s on a small body of water. Phosphates are food for algae but not he only source. I've made a couple of videos that can be seen on YouTube and my site on the "Chemistry" page. You can watch both of them there.

The CYA is probably high because you're using stabilized chlorine, either sodium dichlor or trichlor. Check the ingredients on the package. Unfortunately there's no other way to reduce the CYA but through a partial water change. The CYA range is 30 - 50ppm. What happened to you has happened to countless pool owners. You're in a better situation in that you're dealing with a hot tub while pool owners would need to drain 15 - 20k gallons.

There are two ways to go with your hot tub. First is to get the CYA to 30ppm and keep the FC up

between 3 - 5ppm. FC is eaten up very quickly by heat so keeping it a bit higher is good. The pH and TA are kept at 7.2 - 7.6 and 80 - 120ppm. The 2nd way is to use bromide as your sanitizer. It has a better heat resistance than chlorine. However, it takes a little finesse. You need to make a "bromine bank" then add chlorine to activate the bromide to covert that into bromine.

You'll also need a kit that measures bromine. Taylor K-2106 FAS-DPD Bromine Complete Test Kit is one of the best. I don't sell them nor do I get a kick-back and they're more expensive than other kits, but it's worth it.

Hot tubs are just smaller swimming pools. The basics are all the same. You have the suction side, the water goes through the filter, then is returned back to the tub. Chemistry is the same. What you're dealing with is a less forgiving body of water. Pools that are 20k gallons are much easier on chemicals than a 500 gallon hot tub. With hot tubs the FC can bottom out quickly due to the heat (as was mentioned) and 4 - 5 people in a hot tub will eat up chemicals. 4 - 5 people in a pool, no big deal.

For reading, I would recommend my eBooks that can be found on my site. All of the information about chemistry is the same. I go into tremendous detail about products and chemicals. Exactly what to look for and what to avoid, and why. I'd also encourage you to watch the videos, look at the before and after pics, and read the testimonies. They're from pools that I've cleared up and have helped through phone consults. That's the big thing here. Everywhere you go you'll have people "telling" you something about something, but, do they have the proof to back it up?


Robert