Have Been Using Dichlor For Past 4 Months

[jasonw]

On instruction of my spa dealer I have been regularly using dichlor for sanitizing of my tub. Now 4 months in I am beginning to experience problems with the tub requiring more dichlor to prevent cloudy water due to what I'm assuming is algae growth. I've been reading through the forums and realize now that I should've been using chlorine bleach opposed to dichlor. My question is this; I assume that the CYA levels of the tub are very high (I don't have a CYA test kit) if I swith to bleach now will these CYA levels drop off and allow me to regain control, or am I further off just to drain and start new.

Thanks

[chem geek]

Unfortunately, the CYA level does not drop on its own and the only way to reduce it is through dilution so you really need to drain and refill to start over. At least now you know and can just use Dichlor for about a week, assuming you add about 2 teaspoons every day to 350 gallons, and then switch to using unscented bleach at around 3 fluid ounces (for 6% bleach) every day, assuming that's enough to handle your bather load. You should get yourself a good test kit such as the Taylor K-2006 (not the K-2005) here or the TF100 kit here.

Be sure to add the bleach slowly over a return flow with the jets off (or on low so the bleach doesn't splash or aerate). For extra safety, you can take a bucket you fill with spa water, add bleach to it, mix, then add this back to the spa slowly (this probably isn't necessary, but if you can't add the bleach very slowly or make sure it gets well mixed in the spa then this is an alternative).

Technically, there is another alternative if your CYA level is high and that is to raise the FC higher, but for a high CYA level this would be a ridiculously high FC level. For example, if the CYA were 200 ppm, then the FC would need to be 40 ppm to be equivalent to 4 ppm FC with 20 ppm CYA. Though you could do this using the bleach, people will think you're nuts even though the disinfecting chlorine concentration would be the same. Besides, a drain and refill is probably in order after 4 months anyway, just to remove the buildup of organics that haven't completely been oxidized (if you don't have an ozonator, then even using MPS doesn't completely oxidize organics -- it just makes them more soluble or sometimes volatile).

What is the size of your tub and how much Dichlor did you add (say, in teaspoons) and how often did you add it? You are right that cloudiness and unusually high chlorine demand are signs of algae growth. Do you keep your spa covered? How much light does it get (hours per day)?

Richard

[jasonw]

Thanks for all of the helpful information. The tub size is 375 gallons. Usually I add a tablespoon of Dichlor everyday after use, but over the last few weeks I have been using considerably more to combat cloudy water issues. I shock with MPS every 5-6 days, and have no ozone system. The spa is covered and only used in the evening so it recieves no sunlight.

Thanks again for all of the help

Jason

[Hillbilly Hot Tub]

On instruction of my spa dealer I have been regularly using dichlor for sanitizing of my tub. Now 4 months in I am beginning to experience problems with the tub requiring more dichlor to prevent cloudy water due to what I'm assuming is algae growth. I've been reading through the forums and realize now that I should've been using chlorine bleach opposed to dichlor. My question is this; I assume that the CYA levels of the tub are very high (I don't have a CYA test kit) if I swith to bleach now will these CYA levels drop off and allow me to regain control, or am I further off just to drain and start new.

Thanks

If water changes are done every 3 months (or more depending on spa use) as suggested by manufacture and chemical companies, the CYA would not get so high.

[chem geek]

Jason,

One tablespoon of Dichlor in 375 gallons adds 5.5 ppm FC and 5.0 ppm CYA. So every month the CYA would increase by 150 ppm and after 4 months it would be near 600 ppm (even after 3 months it would be near 450 ppm). At any rate, that's way, way too high. Though algae is one possibility, another is that the organics and ammonia/urea have built up because there is so much CYA that breakpoint is slower. Either way, the solution is the same. A drain/refill.

Richard

[Hillbilly Hot Tub]

Jason,

One tablespoon of Dichlor in 375 gallons adds 5.5 ppm FC and 5.0 ppm CYA. So every month the CYA would increase by 150 ppm and after 4 months it would be near 600 ppm (even after 3 months it would be near 450 ppm). At any rate, that's way, way too high. Though algae is one possibility, another is that the organics and ammonia/urea have built up because there is so much CYA that breakpoint is slower. Either way, the solution is the same. A drain/refill.

Richard

Closed spa with no sunlight....not algae, 4 months, nightly use in 375 gallon tub...need to drain.

[TinyBubbles]

I've read alot of people say that algae isn't a problem in spas. Hot tubs are not used only in the dark. We use ours on the weekends with bright sunlight and in the evenings before the sun has set. From what I understand, algae thrives in warm water. So, why do people say no algae in spas. Does algae require more than 6 to 8 hours of sunlight a week to grow?

[chem geek]

No, algae doesn't need that much sunlight to grow, but with less sunlight it grows less quickly. Though algae likes warm water, most algae does not like hot water as found in spas (104F). So algae in spas is unusual, especially if they are covered. Hillbilly Hot Tub is right that in this situation it is very unlikely to be algae since its covered most of the time and only open at night.