How Often To Shock...?

[mraybone]

Hi all! So I've got my tub running nicely again after an Ahh-Some clean. I know now to shock after use, but I was wondering how often I need to shock if the tub isn't used, whilst keeping chlorine levels consistent, obviously?

[eaquacare]

Some people shock spas on weekly basis - heavy users, for someone who is not going to use it that often, you can be good with once a month (which is a good practice)

There are two types of shock for Pool and Spas Chlorine Shock (Sodium dichlor) and Non Chlorine Shock (Monopersulfate), Both are used to sanitize the water to kill accumulated bacteria/algae or microbial growth. The chlorine based products are used for startups and eliminating organic waste or cloudiness of water, where as the Non-chlorine shock is what people generally use for regular maintenance.

Frequency would depend on use and i would recommend to follow instruction on the branded product you end up using.

Good luck.

[chem geek]

It also depends on the method of disinfection you are using. Shocking is required more when using Dichlor-only due to the buildup of CYA over time and it's also needed with the Nature² with MPS system since shocking with chlorine every week or so is usually needed to keep the water clear. With the Dichlor-then-bleach method, however, shocking is not normally needed since you add the proper amount of chlorine after a soak to handle the bather waste and have a residual in time for the next soak. The water stays in good shape for longer -- about twice as long compared to Dichlor-only.

[bill p]

Hi I have a question I am using the bleach method with my new spa I have had great success for years with my above ground pool, but I do have a few questions regarding it use

in my spa. I added CYA with first filling of the tub 450 gallons and have the level at about 30-40 ppm. I keep the chlorine at a daily level of 1-3 ppm and that's with adding about 2oz

after each use, but I have been noticing that chlorine smell lately does this mean I need to shock and does shock mean to like 10ppm for 24 Hours like with a swimming pool?

and would I want to shock it with regular bleach or one of the non chlorine types I am reading about? any info would be much appreciated

[chem geek]

2 fluid ounces of 8.25% bleach would only handle around 20-30 person minutes of soaking in a hot spa unless you have an ozonator and use the spa daily. Is that your situation? So at the time of your next soak you have 1-3 ppm FC? I suspect you might not be adding enough chlorine to handle your bather load, but if you measure an FC residual before your next soak then you should be OK. Also, if you start your soak with 1-2 ppm FC then there should be less chloramine smell, but after you dose with chlorine after your soak there will most certainly be smell and if that is what you are talking about then that is normal and why it is better to have the cover off during the immediate time after you dose after soaking.

I'd just keep the cover off longer after you dose after your use. And you can open up the cover before you soak for a short time to air out any buildup of chloramines. If you want to try elevating the chlorine level, then yes just raise it to around 10 ppm for a day, but normally you should not need to do this just as with a properly maintained pool you should not need to shock. I haven't shocked my pool for years, but maintain a minimum FC that is at least 7.5% of the CYA level (for a spa the minimum isn't as critical since a covered hot spa rarely gets algae).

[bill p]

Thank you for your response, I do not have an ozonator although the spa did have one (pervious owner removed) I still don't quite understand the pros and cons of having one. I am sure there are many posts on that subject. so anyway what I normally do is get out of the tub dose and than close the cover pretty much right away NG right that is keeping the chlorine gas in ? and I will try opening 10 minuets or so before getting in easy enough, but at least I know its normal.

[chem geek]

For a chlorine spa, an ozonator works well if you use the spa every day or two because the ozone helps to oxidize the bather waste so you use less chlorine and produce fewer chlorinated disinfection by-products. However, if you do not use the spa regularly, say only on weekends, then an ozonator results in a higher daily chlorine demand in between soaks because ozone and chlorine react with each other.

[mrwrick]

Chem Geek, your last reply to this thread gives me some more information about adding an ozonator to my vacation spa. I would like your opinion. The spa gets used every week or maybe not until 2 weeks by 2 to 4 bathers 20 minutes each per day on the weekend, if that (it may be 2 bathers twice a day, seems the same bather load to me as 4 once a day, the likely pattern). Dichlor used initially after fresh refill, CYA level at 30-40 ppm, and chlorine added after each soak (also before if test indicates low FC) . Given the weekly/biweekly time lag between uses is an ozonator going to help or hinder maintaining adequate FC in the tub between uses? It sounds like it will deplete more chlorine than we can afford to lose during the down time.

My next question is about CYA depletion. In another forum I read your comment that chlorine actually reacts with and dissipates CYA about 5%. Over what time span will that occur? If that is a regular rate it may influence me to continue using Dichlor more frequently to help hold a bit more FC in the tub during the lag times (when leaving for a week or 2 when daily testing and bleach additions will not be done). Does this sound reasonable and effective? This may also influence me to avoid installing a SWCG for better chlorine disinfection during the lag times. What is your opinion on this subject? Let me know if this is worth another thread. Thanks for your thoughtful help always.

[mrwrick]

I reread the notes I made about CYA oxidation. You referred to 5 ppm per month, not 5%. Thanks for opinions.

[chem geek]

The 5 ppm CYA per month loss is for usual chlorine and CYA levels so around 2-4 ppm FC with 30-40 ppm CYA.

Yes, the ozonator will increase your chlorine loss significantly, but even with no ozonator it will be a challenge to keep chlorine over two weeks. What would help is lowering the water temperature, but in a spa even the circulation pump will warm the water. While it's not difficult to raise the chlorine level to last for a week with no ozonator, it would be hard for 2 weeks.

Perhaps you should use bromine instead of chlorine in which case the ozonator would maintain a background bromine level if you added sodium bromide initially to set up a bromide bank.

[mrwrick]

Thanks Chem Geek. I have considered bromine for just this reason. The interaction is something someone of your expertise needs to explain to me. Thanks for the tip that the ozonator will add to effectiveness and length of bromine. What about the SWCG system by ControlOmatic, the Chlor=Maker?

[chem geek]

An SWCG system would also be an option and let you use chlorine. With either the ozone/bromine or the SWCG/chlorine methods you need to be careful to not overshoot and get the bromine or chlorine level too high. So you'll need to experiment to see that in between visits you tune in on-time so that the disinfectant level remains stable and not too high -- probably around 2 ppm FC for chlorine and 4 ppm for bromine. Don't forget that with chlorine even from an SWCG you should start out with 30 ppm CYA in the water so that the active chlorine level isn't too strong.

[mrwrick]

I read through a long thread that discussed one particular SWCG system with a fairly large amount of naysaying and comments about marketing being the focus over effectiveness, sales numbers vs. results. It was not the ControlOmatic ChlorMaker. Is there one SWCG that is most highly rated for effectiveness and reliability? PLease share your opinions about what to buy or avoid in the SWCG market. Thanks

[chem geek]

That wasn't a standard SWCG. That was about the HotSpring® ACE® Salt Water Sanitizing System which uses boron-doped diamond electrodes to produce more hydroxyl radicals in addition to chlorine. That is more susceptible to wear and requires a low CH level (50 ppm or lower). That is not the same as standard SWCG systems such as the ControlOMatic TechniChlor that I don't believe has the same failure rate.

[mrwrick]

Thanks for the straight scoop. So, ozonator with a bromine system for the spa that will sit the longest between test/adjustments/use, and standard SWCG with a chlorine system for the spa that will sit but not as long, hopefully no longer than a week between test/adjustment/use. Would that be an accurate plan for the 2 spas that will sit between one and 2 weeks between attention?

[chem geek]

Not exactly. Ozone with bromine and SWCG for chlorine are comparable in terms of maintaining a residual between soaks and will do so for quite some time but with the risk that you need to tune it in so it won't get too high or too low. My comment about one week max was for chlorine with no ozonator when manually dosing -- not with an SWCG. You could manually shock the spa with chlorine to last a week if the water temp isn't too high, but probably not longer than that.

[mrwrick]

So, a chlorine spa with a SWCG system in place, a recirculation pump running 24/7 but no jets, being shocked before leaving for one week, temp turned down to mid-90s. Can I expect it to receive adequate chlorination from the SWCG without being manually adjusted for one week to maintain a 1ppm free chlorine reserve? If so, it too far a stretch to say it is reasonable to expect it to be able to maintain the sameFC reserve for 2 weeks if all else remains the same, lower temp, no use, same recirc pump but no jets, no added chlorine? I hope I am getting close to a point where the system can be at its best taking care of itself so that i do not have to try to send someone in to this somewhat remote location for periodic testing and adjustment. Thanks for helping me refine the plan.

[chem geek]

With an SWCG it in theory can maintain the FC level for a very long time. The problem is dialing it in so that the FC production from the SWCG equals its loss/usage and that can be tricky to do. Fortunately, the loss is usually a percentage of the FC so there's a negative feedback effect that prevents too much of a runaway effect, but I've seen posts from some indoor SWCG pool owners who didn't check frequently enough and ended up with way too high FC.

When I was referring to lower temps, that's to lower the chlorine usage when manually dosing so that the chlorine lasts longer. This isn't so relevant for an SWCG. The lower temps would let you turn down the SWCG on-time lower, but at higher temps you should still be able to maintain the FC level with a higher SWCG on-time -- you just wear out your SWCG faster that way.

I think you'll just have to experiment to see how you'll do maintaining the FC level with the SWCG.

[mrwrick]

Thanks again. It sounds worth a try to put in a SWCG and do the adjusting. It cannot be any less effective than what we are doing currently using Dichlor for shock method when we arrive and leave, bleach method during use periods and turning down temp during absences.

[Spanky]

Properly dialed in a Chlormaker SWCG can maintain 2ppm FC for weeks on end but you do need to be careful it doesnt climb too high. Another advantage is that other than an extended power failure it is virtually impossible for the FC to drop to and remain at 0. The cell cycles on every 3 hours and makes chlorine. Start out with a power level of 2-3 then check the FC as soon as you return then adjust the power level up or down depending on what you measure. It is important to check before anyone uses the tub. After each use, dose the tub with chlorine (bleach) just as you would with Dichlor/bleach method. Yes people will chime in and say that you can simply use "boost mode" and do not need bleach, but excessive use of boost makes. dialing in difficult and shortens the life expectancy of the cell. At lower power levels, the cell should last 3 or more years easily. Replacement cell for Chlormaker IL is $106.00, about $35.00/year (Less than the average cost of 1 tub of Bromine tabs!!!)

[mrwrick]

Thanks Spanky, that is encouraging news. I feel confident I can dial it in and make sure my co-owners watch it carefully as well. We are family and all motivated to maintain this spa while not being able to be there everyday and often for a week, sometimes 2. It is our vacation home and everyone involved wants to be able to walk in, measure FC, make an adjustment, turn up the temp and take a soak within a couple hours. We had a so-called spa maintenance guy for years who supposedly came by every other week to service this spa for our elderly parents. But he let the water go to green slime and then recommended we replace the old spa. We canned him, saving $60 per month, and got the tub back to clean and working largely through the good advice and help from this forum's spa categories and all of you knowledgable and willing people. The addition of a Chlormaker SWCG should give us just the cushion of confidence we need to keep the spa up between our visits. I am also dealing with a spa I expect to run on bromine when I get it done and the ozonator advice will be applied there. Thanks again to Chem Geek, you and all others who have read our questions and freely given consistent advice.