New Spa Owner - Dichlor/Bleach Method Question

[crwells]

Hello All,

New to site and a spa noob. Lets start by saying this site is welll appreciated and enjoy learning from the experience of others.
Other than this site, I haven't found anyone locally that really seems to know spas. It seems like everyone has a different opinion on how to properly sanitize and their opinion correlates to the directions of the product they are trying to sell me, but not their experience.

I have read the chlorine article by Nitro and can attest to the method of reducing TA as of last night when I changed and refilled my spa because of an overreaction to high combined chlorine, which caused CYA thru the roof.lol No worries, the learning part is fun as long as no one gets itchy or sick. Without knowing, I had allowed my free chlorine to get to 0 for too long. Since then, I have purchased a Taylor kit, read everything I could, and feel that I have a decent grasp on water balance and sanitization. I haven't figured out what saturation has to do with it all yet or that dial that came with the kit, but will find something to read on it when I get the chance.

My Spa: is a 485 gallon Master Spa with ozonator and 24 hour recirc.
Usage:We are starting out as weekend warriors in the spa with exception to my son getting in several times a week after hockey.

I would really like to use the dichlor/bleach method, however there are times that I travel a lot and would struggle to keep the FC up during non-use. I noticed that chem geek has posted several times that the combination of ozonator and low use may make this method too much maintenance.

Now to the question,
Is it possible to be a hybrid,
1 add borates to balance ph
2 use dichlor or 1" trichlor floater until CYA gets to (X)
3 then use clorox on heavy use or when I am available to check and maintain FC every day.
3 go back to dichlor or 1" trichlor floater when the spa will sit for traveling / vacations etc.
4 Side note, do you still shock with oxidizer with this method or can you still.

I figured, since I had just refilled and balanced, this might be a good time to develop a strategy this time.
I have a feeling that my responses will be to go to bromine, but I don't like the smell of it.

Any thoughts are greatly appreciated. :-D

 

[chem geek]

You usually cannot use Trichlor in a spa because in the hot water it dissolves too quickly so the FC level gets too high and the pH too low as a result. There are a couple of systems with special feeders that use Trichlor (see "335 Chlorine / Bromine Floating Dispenser" in this link as one example), but most spa manufacturers void their warranty if you use Trichlor. It's up to you if you want to go that route -- you just have to be careful, especially at first until you get an idea for how quickly the chlorine is dispensed and its effects on FC and pH. Note that the TA will drop and need to be restored with baking soda on occasion and you would keep the TA level higher than with the Dichlor-then-bleach method.

If you want to avoid bromine, you can see if you are interested in using the ControlOMatic TechniChlor which is a saltwater chlorine generator. Some spas may not have components that are corrosion resistant enough at higher salt levels, but most spas do OK. Another alternative is to use Nature² silver ions with non-chlorine shock (MPS).

Yet another alternative would be for you to figure out how to turn off your ozonator, though you'd still not be able to go longer than a week with chlorine if you raised it to fairly high levels (it will last longer if the water temperature is allowed to drop in between soaks).

You don't want to use Dichlor unless your CYA is too low. If you need fast chlorine and your CYA is already high enough, then use bleach. The Trichlor would only be for background dosing in a special feeder as I noted.

You don't need to shock with the chlorine methods. With bromine, you sometimes need to use chlorine on occasion to keep the water clear and the same is true for Nature²/MPS as well.

 

[crwells]

Thank You for your feedback.

My spa vendor warranty states that it doesn't cover any Trichlor shell damage from tablet exposure. So based on your feedback, here is my plan.

Use dichlor until I get to target tested CYA of 30-40. I have one of the 1" trichlor floaters for spas, it allows you to screw in the feed tube and lock it in, leaving as small of a sliver as you want. I will adjust it to only keep up with non-use consumption (maintain .5-1ppm) generated by ozonator. Then after spa use and FC gets used up, I will bleach to 5 ppm, or whatever you think is ideal. All of this, knowing that I will have to pay attention to PH/TA, the Taylor kit makes this very easy. Being an electrical engineer, I find the chemistry side of this very interesting and a fun change of pace to keep track of. I am playing with the Pool Pal app now.

Questions:
Is that realistic?
Do I still stabilize TA and PH with boric acid?
Do I still try to achieve 30-40 CYA, then bleach or forget Dichlor altogether, knowing that the Trichlor is adding CYA in its self. Hopefully, I can get 4-6 months for re-fill.

My current Levels yesterday were:
ph:7.4
TA:90
CH:150
FC-3-5
CYA: haven't checked it since it is a new fill. Only a tsp of dichlor has been added.

 

[chem geek]

Yes, it's reasonable. Try and tether the floating feeder so it is away from the walls. That's what they are concerned about -- that the feeder parks itself in one place and that the dissolving Trichlor lowers the pH nearby and the high chlorine at low pH damages the spa surface. When I first got my pool years ago, I had a floating feeder with Trichlor pucks that parked itself near some stainless steel mounts and they rusted. It's a serious problem, so either you always have to have water circulation or you need to keep the feeder away from spa surfaces.

Boric acid is more useful when you are not using net acidic sources of chlorine since it tends to buffer more strongly against a rise in pH. When using Trichlor that is acidic, then a higher TA is generally more helpful since the outgassing of carbon dioxide tends to keep the pH up. Borates will buffer pH, but they don't buffer as strongly as the pH gets lower -- the carbonates are better for that.

As for CYA, you should still start off with some, but perhaps only 20 ppm from Dichlor and then let the background Trichlor slowly have the CYA creep up. The CYA also slowly breaks down from chlorine at around 5 ppm per month at usual spa CYA levels so perhaps your Trichlor won't build up the CYA too quickly. You can always add Dichlor when needed to raise the CYA quickly.

As for the FC level, you just need to make sure it doesn't get to zero at any time. Most people target around 1-2 ppm FC at the start of their soak as that minimizes the chlorine/chloramine smell. You then add oxidizer (usually bleach) after your soak to handle your bather waste. The Trichlor would then be for background dosing.

 

[crwells]

Awesome. Thanks.

My Floater wants to hover in front of the skimmer. I also have a 24hr recirc. pump, I wonder if that will prevent too much camping. I will pay close attention and will look for a way to tether it in the center of the spa.

Thanks again.

 

[chem geek]

If the circulation pump is always on and the Trichlor is near the skimmer, then that's probably OK since the pH shouldn't drop much if you've got the feeder turned way down -- and it should be way down since the circulation should dissolve the tabs more quickly. You could always measure the pH downstream near the pump or from a return to see if there's any noticeable drop -- I'll bet it's not even measurable.