Adding CYA--is it just to reduce chlorine use?

[davethomaspilot]

I just started using Intellichem to constantly inject chlorine to regulate ORP. For the last six months, I've been running with no daily chlorine at all, just weekly chlorine in the form of shock + constant ozone injection and copper ionization.

Right now my CYA is zero and the ionizer is turned off.

I figured I wait to add the CYA--this should require more work from the Intellichem and I want to see it "doing it's thing".

Intellichem regulated the ph down to my setpoint of 7.4 and ORP up to 700. ORP = 700 resulted in more FC than I want, so I've backed it down to 680 and will test again tomorrow morning.

The pool gets full sun and the last two days have been sunny, but today is cool.

I was expecting chlorine use of around a gallon each sunny day (17K gallon pool) after reaching the initial FC target. It seems quite a bit less than that so far, but it's too early to get an accurate measure. I'll know better after a week of use and daily (afternoon) FC measurements.

I think I paid $1.39 per 64 oz bottle of 8.25% bleach at Aldi. The canister holds four gallons. Before I add CYA, I want to figure the cost and required refill frequency if no CYA is used at all. Then go from there.

Are there reasons to use CYA other than reducing chlorine usage?

Thanks!

 

[pabeader]

CYA is actually to buffer the effects of chlorine on people, suits, pool equipment and liners. It also, else buffer the effects of UV breaking down chlorine.

As long as you have your FC dialed down to around .2ppm (if I remember right) you might be okay without it. Most systems aren't that accurate or precise so we suggest some CYA and a higher FC as a safety margin.

 

[jblizzle]

Where is Apex? Update your profile, please.

With 0 CYA, in noonday sun, you will lose 50% of your FC every hour to the sun. You really can not safely maintain an outdoor pool in the sun with no CYA in the water. If you maintain a high FC level, a LOT will be lost to the sun and it will will be very harsh on your skin, equipment, and suits. If you try to maintain a very low FC level so it is not a harsh, it will disappear to the sun and use and leave the water not safely sanitized.

 

[davethomaspilot]

Updated my profile--thanks for pointing out I omitted the state.

You really can not safely maintain an outdoor pool in the sun with no CYA in the water.

Are you saying the chlorine doser won't be able to keep up with the loss of FC?

It's having no problem with regulating the ORP and I was going to( keep) checking the FC mid-afternoon to make sure it stays in target as the days get hotter

Being harsh on skin, equipment, and suits is a different argument.

I do plan on adding CYA, just trying to determine what's optimal for my situation and why.

 

[jblizzle]

It may keep up but will waste a massive amount of chlorine.

Put the CYA at 30ppm to at least get some protection and hopefully not impact the ORP (which I really do not recommend).

 

[YippeeSkippy]

Your addition of copper is also playing in to this. The ionizer is pretty worthless on its own in outdoor pools.

Are you aware of the problems adding metals to your pool causes? Particularly stains and green hair.

 

[davethomaspilot]

Yes, I'm aware of the staining and green hair risk associated with adding metals.

I'm going to slowly raise the CYA level from zero to whatever is required to maintain the recommended FC level based on FAS-DPD tests. First step is to measure the actual depletion at CYA = 0.

Yesterday, I didn't see a measurable degradation in FC between 4:00 and 4:30 in full sun. I'm going to test at 12:30 and 1:30 (sun directly overhead) for a few days.

Today is cloudy, so while I'll get another data point there's not much UV.

 

[pooldv]

CYA also significantly buffers the harshness of chlorine making it much more pleasant to swim and much easier on hair, bathing suits, etc. We have CYA at 70-80 for our saltwater pool. We were SLAMing to get rid of a little algae last summer, our shock level was 28 ppm. We swam every day for a couple of weeks with chlorine at 28 ppm and nobody even noticed. Except for the guy driving the FAS/DPD test.

Here is chart showing how CYA reduces the harshness of active chlorine, http://troublefreepool.com/~richardfalk/pool/HOCl.htm

You can see in the table that with a 0 CYA and a FC of 5ppm ... the active level is 2.4ppm. At a CYA of 50ppm, you would need the FC to be up around 40ppm to be the same active level.