BBB and Spa

[morettina]

We recently bought a house with a pool and spa, and are having no problems with maintaining the pool. However, we are having trouble with the spa, and have decided that it's probably time to empty it and start from scratch.

Can anyone tell me if there's a particular order that we need to follow to add BBB to balance the spa? I do have a container of chlorine powder that I can use in the spa, especially if it will help get things up to speed quickly, but after that, hope to use only BBB, and the powder only when we know we won't be around due to travelling. When we first bought the house, we were able to bring chlorine up to about 10, lower the temperature, and could go away for a few weeks and not have any problems.

Thanks for any help.

Marie

 

[chem geek]

You basically use Dichlor as your chlorine source until you've cumulatively added around 33 ppm Free Chlorine (FC) (usually around a week or so) and then you switch to using 6% unscented bleach after that. You should have your Calcium Hardness (CH) lower than in a pool -- around 100-120 ppm is usually OK and not more than 150 ppm. You should have your Total Alkalinity (TA) be low -- no more than 80 ppm -- and can be as low as 50 ppm if necessary after you've switch to bleach if you find the pH rising. See Using Chlorine in a Spa for more details.

If you go away on vacation, you don't use powder and would still use the bleach, but would do as you did before raising the FC and lowering the temperature. You would likely have to shock upon return as I doubt 10 ppm FC would last much more than a week unless the water temp got quite cool.

 

[PaulR]

Welcome to the forum, morettina!

I'm doing pretty much what chem geek described in my spa and been very happy with the results. Although I think burning through 33ppm FC in a week takes some doing (5ppm per day ); I'm usually on the dichlor regimen for 2-3 weeks after a refill.

Speaking of which... It is generally recommended to drain and refill the spa periodically; there's a formula but for most people with a home spa it works out to probably every 3-4 months. The problems you were noticing that led to a refill might just have been because you were reaching that point. I know my spa starts to get cranky, using a lot more chlorine than usual, when it's really time to refill.
--paulr

 

[chem geek]

I was figuring roughly 4 ppm FC per day which in 350 gallons would handle around a half-hour of one person soaking or two people for 15 minutes every day. If it's just one person for 15-20 minutes, then the chlorine usage would be lower and it would take 2+ weeks of Dichlor as you say. This also depends on temperature. For a hot 100-104F spa, the rough rule of thumb, independent of spa size, is that it takes around 3-1/2 ounces of Dichlor or 5 fluid ounces of 6% unscented bleach for every person-hour of soaking to oxidize the bather waste and last for some residual the next day. Of course, this is a rough guide and your mileage may differ.

The standard Water Replacement Interval (WRI) is (1/3) x (Spa Volume in Gallons) / (# of people) where the assumption is roughly a 20 minute soak. So for a 1 person 20 minute soak in a 350 gallon tub, this works out to 3-4 months. However, most people using Dichlor-then-bleach find they can go almost double this time before they feel they need to change the water, but again your mileage may differ.

 

[morettina]

Thank you everyone for your replies. We are heading to our house tomorrow and I've printed everything out to take with me. When we are not there, we turn the temp on the spa down as far as it will go. This time of year, it tends to hover around 80-85 degrees even with the setting at 59 just because the air temp is higher, so the temperature isn't kept at typical spa temperature every day. We could never afford the electricity for that!

When we first bought the house, we were able to leave it with the chlorine levels around 10, and turn the temperature down, and 3 weeks later, the chlorine would be just about right for use. Since we're not living at the house full-time yet, we haven't used it very much (maybe a few dozen times), and figure that we're right around the mark of having used it about 3 months (even though we've owned the house for much longer). Right now, no matter how much Dichlor I dump in there, the chlorine is still testing at 0. So we're going to be learning how to empty and clean it this coming week, and will start from scratch with chemicals.

The pool has been easy to manage, but for some reason, I've had more trouble keeping spa chemicals balanced. We do have a full Taylor test kit, so the one thing I've gotten very good at is testing. We discovered very quickly that test strips were useless.

Thanks again.

Marie