Trying to reconcile different CYA recommendations

[VinceL]

Even though construction continues for our elevated spa, the pool is running. I have started using my test kit, and have been going through Pool School another couple of times.

I am trying to reconcile the different recommended CYA levels that I have seen. In Pool School it states "If you have a SWG or very high levels of direct sunlight, CYA is typically kept between 70 and 80. If you are using an ORP controller, keep CYA below 50." Well, we have an SWG, very high levels of sunlight (pool in direct sunlight all day with no shade), and an ORP controller. I didn't find any information in Pool School that explains why the CYA needs to be below 50 for an ORP controller.

The manual for our ORP controller (Hayward Sense & Dispense) says to use the recommended levels in the Pro Logic manual. The Pro Logic manual specifies a recommended CYA of 60 to 80.

So, where should I be keeping my CYA? :?

 

[jblizzle]

I think the reports of the ORP acting erratically with CYA above 50ppm pretty much trump all other recommendations if you want it to function. There are members who have abandoned the ORP sensor since it would not hold a constant FC level and gone back to time based generation. It just seems that the ORP method does not work very well for outdoor pools in some cases.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[chem geek]

You'll just need to make sure your SWG is sized large enough to keep up with the higher chlorine demand that will result from having the CYA by 50 ppm instead of 80 ppm. Also, your pH will tend to rise more quickly due to the higher SWG on-time (so more outgassing).

 

[VinceL]

Thanks for the replies.

The pool is listed as 13,700 gallons and the spa is 500 gallons. I went with the T-Cell15 rated for 40,000 gallons. I had figured oversizing the chlorinator would allow it to work less and hopefully last longer. So, I think (hope) I should have the chlorine generating capacity to keep the FC in range with a CYA of 50.

 

[chem geek]

The SWG ratings are woefully inadequate and are usually on the order of 0.3 to 0.4 pounds per 24 hours in 10,000 gallons which is only 0.167 ppm FC per hour output. Your oversizing gets you to around 0.5 ppm FC per hour which should be sufficient even at 50 ppm CYA.

 

[VinceL]

Thanks, chem geek.

I'm glad I got the big cell...at least I have a chance of making things work with the ORP and CYA at 50.