Trichloro + Cal Hypo to limit CYA buildup

[Ron Stordahl]

Minnesota pool inspectors rules limit CYA to 100 ppm. Above that you have to partially drain pool and add water to reduce CYA. We currently use Trichloro 3" pucks in a feeder to conveniently set chlorine level, but near the end of the season we are close to 100 ppm CYA.

My question..how about adding Cal Hypo along with using Trichloro so as to slow the build up of CYA. If this is a successful approach it would be easy to implement. Does the CYA from the Trichloro provide some benefit to the chlorine use from the Cal Hypo chlorine?

Our season is 4 months. Seems like it would be a shame to have to drain down by half just to finish the 4th month.

Ron

 

[RobbieH]

CalHypo will build up Calcium Hardness (CH) in your pool, which will eventually lead to scaling. Liquid chlorine (bleach) or SWG is the way to go.

You do know you have to raise FC as CYA goes up, right?

 

[woodyp]

That would all depend on you calcium level in the water before trying.

 

[Texas Splash]

As we have learned, chlorine is chlorine but it's those additional chemicals that get us into trouble. Stabilizer (CYA) with pucks and CH with cal-hypo. Yes, you can have pucks in the feeder at times, then switch to cal-hypo other times. Regular liquid bleach is always your best option to prevent those increases.

 

[pabeader]

This isn't a residential pool. So our responses might need to be tweaked a little.

 

[Texas Splash]

Good catch Bob. I skimmed right over that one.

 

[JoyfulNoise]

You can't mix cal-hypo and trichlor in the same feeder. You must add them to the pool using different equipment. Cal hypo is a strong base while trichlor is acidic. If you mix the two directly it can cause an explosion.

Normally trichlor tabs are floated in a blue chemical floater while cal hypo is a powder that is added directly to the pool water and brush mixed.

 

[Ron Stordahl]

My only two chemical options are Trichloro pucks and Cal Hypo granules. I should think liquid chlorine bleach would be too expensive. The pool is in use for a maximum of 4 weeks each summer. My only issue is that near the end the CYA reaches 100 at which point I an concerned the pool inspector will require us to partially drain and refill to lower the CYA. If that were to happen we might simply shut down the season. So my goal was through the use of Cal Hypo to provide enough chlorine but without raising the CYA to the max permitted value.

I should have noted initially that this is a 66,000 gal outdoor pool. The 3" pucks are very convenient, but they do require the use of soda ash to keep the ph in the 7.5 range..which is easy to control.

So to simplify would it be reasonable to use a combination of Trichloro and Cal Hypo with the goal of limiting CYA to 50? I do understand that you cannot mix the two products. The Trichloro is distributed via a erosion feeder. The Cal Hypo would be added as needed using a pail.

If Cal Hypo drives the ph up, perhaps less soda ash to offset the Trichloro would be needed.

- - - Updated - - -

Ops! I meant to say the pool is in use for 4 months (not weeks!) each summer.

 

[tim5055]

It will work as long as you drain down quite a bit during the fall shut down so that you can get rid of the CH that is building up. You may also want to keep a closer eye on your CSI as the CH rises to keep from scaling.

Another thing to take a look at are there regulations you have to deal with regarding manual additions of chemicals. Many states require the pool to be closed a certain number of hours after the manual addition of chemicals.

 

[Ron Stordahl]

When we open mid May the remaining water (about 50% to keep the pool from rising out of the ground) is removed, it's filled with dirty water and rotting leaves, and we start with fresh water.

Yes we can check for CH buildup. However the idea is to use the minimum Cal Hypo needed to prevent excessive CYA buildup.

We will give this a try this year.