Trichlor vs. Calcium Hypochlorite

[Pcmaker]

I'm a CPO for a hotel/casino in Las Vegas and have been for 13 years now. All this time, we have been using Trichlor for both the pool and the spa.

The pool is 38k gallons. The problem is during the Summer it gets so hot, that we max out the Chlorine feeders, constantly pumping trichlor into the pool. It's a manual, Rainbow 300-29x feeder and we have 2 of them for the pool. Trichlor has Cyanuric Acid in it, which lowers pH. The constant feeding of Trichlor during the hottest parts of the summer decreases the pH in the pool and it's a struggle to keep it up to 7.2. We dump in 6 pounds of Soda Ash every morning and it barely gets the pH to 7.2. In the meantime, doing this increases Total Alkalinity to over 200...

The Health Department only allows the Total Alkalinity to get to 120. Anything over and we get a write up in the report.

Columnizing acid doesn't work.. it lowers TA, but it also lowers pH and defeats the purpose.

So, now our local pool supply recommended switching over from Trichlor to Calcium Hypochlorite, which doesn't have Cyanuric Acid. This should fix the problem that we have.

Does anyone here have any experience with Cal Hypo?

Also, aerating the pool as suggested here is not feasible for our pool.

 

[Smykowski]

Switching to Cal Hypo just substitutes a different problem. Eventually, with no water replacement, your CH will get out of control.

I'm not understanding why TA is a problem. In your case, constant trichlor use drives TA down, and keeping it up is usually the problem.

Is an automated liquid chlorine delivery system out of the question? Gas is also an option for large, commercial pools, though I know nothing about them.

 

[Donldson]

If you are able to use borax instead of soda ash you can raise the pH while barely touching the TA. As Smykowski mentioned, commercial pools have more options for chlorine addition than residential pools. It might be worthwhile to look at some of those options before considering switching to cal-hypo. My concern is that if you are using enough trichlor to cause constant pH problems then you will probably use enough cal-hypo to raise your CH extremely fast, which could cause a whole host of new problems.

 

[JasonLion]

There are instructions in the How To section of Pool School on how to lower TA. In your case, you are already constantly adding acid, so all you would need to do is to figure out some form of aeration. The more aeration you can provide, the lower the equilibrium TA will end up being.

 

[Pcmaker]

Switching to Cal Hypo just substitutes a different problem. Eventually, with no water replacement, your CH will get out of control.

I'm not understanding why TA is a problem. In your case, constant trichlor use drives TA down, and keeping it up is usually the problem.

Is an automated liquid chlorine delivery system out of the question? Gas is also an option for large, commercial pools, though I know nothing about them.

The TA does not decrease along with the pH. The water gets backwashed and filled every day to keep CYA around 50 ppm.

 

[JasonLion]

When you add an acid, it lowers both PH and TA (always). Soda ash raises both PH and TA, but it raises TA proportionally more, compared to PH, than acid lowers it. If nothing else is going on (usually something else will be going on), the TA will creep up if you hold PH stable. Aeration will raise PH, without raising TA, which can be used to get things back into balance.

 

[freqz]

Cal Hypo just means you'll be flushing water to lower CH levels instead of CYA and TA.

Why is Sodium Hypochlorite (bleach) not an option? The only thing that leaves in the water is salt...

 

[Pcmaker]

I'd rather take a high calcium lvl than a low pH level. The health department doesn't check for calcium levels. I'd rather have an automated liquid chlorine feeder, but my boss doesn't want any automated feeders for the pool for some reason.

 

[JesseWV]

You can't just let your CH go through the roof. Eventually you will have scaling. It won't require the health department's test kit to see, it will be plainly obvious to everyone.

 

[JesseWV]

If you're back washing and filling everyday to keep CYA down at 50 you're likely wasting tons of water, which I'm sure is at a premium in Vegas.

Using a liquid chlorine injection system would prevent the water waste AND stop your ongoing TA and pH problem!

I would figure out how much it's costing to run the pool now, then compare that to the cost of a new liquid chlorine system. You're likely going to save quite a bit, so let the money talk to your boss.

 

[Rocco]

Where I work they offer several courses for job growth, during one of the courses we covered situations like this. If your current approach with your boss is not working it is recommended that you change your approach to talk about what your boss finds important. As stated above maybe changing your approach to discuss why a change is good for him (cost savings, budget, etc.) instead of why it is good for you or the pool you may get better results.

This of course is all speculation on how you are currently presenting your case, for all I know you can already be taking this approach.

 

[chem geek]

Basically, with Trichlor since it is acidic if you want to raise the pH back up so you also end up at the same TA and not higher, then you can't use soda ash (sodium carbonate) and instead should use a pure base. If you can use borax, that's an option though would increase borates over time (but with your water dilution it should get limited), otherwise lye (sodium hydroxide) would work but is probably not available to you (it's VERY hydroscopic -- absorbs water from moisture in the air).

Cal-Hypo, as with any hypochlorite source of chlorine, will be more pH neutral after accounting for usage/consumption, but will increase CH over time. You'll have to limit that with water dilution just as you have been doing to keep CYA in check, BUT you'll waste less water. The reason is that with Trichlor, every 10 ppm FC added 6 ppm CYA while with Cal-Hypo every 10 ppm FC adds around 7 ppm CH. BUT your CYA level you were keeping down was at around 50 ppm while the CH you can have up at around 300 ppm. So if you were adding 5 ppm of CYA before, you'd have to dilute 10% to get it back down but the same amount of chlorine may add 6 ppm CH and you'll only have to dilute the water by 2% to get the CH back down. So in that sense, you should waste a lot less water using Cal-Hypo.