CYA levels down to zero at every opening

[stslimited84]

As the title states, every year when I open the pool, the cya levels read zero. What is happening to it? Is this normal during the off season while it's closed?

Secondly, the ph always rises really high in the off season and it's causing the plaster to get rough. Is there any way to prevent this from happening in the off season? I want to install a second stenner to auto dose acid into the pool to keep it slightly lower on the ph scale to eliminate the roughness of the plaster and reduce time spent adding muriatic. Has anybody done this?

Thanks!

 

[IceShadow]

I don’t know why but my pool drops to 0 CYA in winter as well. I just add some in the spring. ( Two year pool owner.)

I don’t know that I’d want to have acid running into a pool on regular intervals when the pump wasn’t running and mixing it up. But maybe I’m wrong....

 

[stslimited84]

The pump would be running during dosing.

 

[IceShadow]

OK - would probably work then, if you get it dialed in. Frequent testing to make sure you don't overshoot on the acid.

We have to drain out pipes for the winter for fear of freezing here

 

[Donldson]

There are several reasons you might open to zero CYA. It can be one or any combination of them.

Natural CYA degredation - CYA does break down very slowly and in the cold even slower, but it can be a part of the losses.
Fresh water - You drain some water and replace it in the spring, this will reduce any CYA left at that time.
Bacterial infestation - There is a bacteria that consumes CYA and excretes ammonia. Worst case this remains in the water creating a very high chlorine demand in the spring. Best case is the nitrogen cycle continues and the bacteria converts the ammonia to nitrite and then nitrate, rendering it mostly harmless.

 

[Oly]

I too have had low CYA levels in the early spring for the last 3 years. I respond by adding only enough CYA to increase levels by 10ppm and recheck after several days as I work my way back up to 40 ppm. I also use several trichlor tabs and calculate the expected results of the added CYA and lowering pH while adding free chlorine.

 

[stslimited84]

There are several reasons you might open to zero CYA. It can be one or any combination of them.

Natural CYA degredation - CYA does break down very slowly and in the cold even slower, but it can be a part of the losses.
Fresh water - You drain some water and replace it in the spring, this will reduce any CYA left at that time.
Bacterial infestation - There is a bacteria that consumes CYA and excretes ammonia. Worst case this remains in the water creating a very high chlorine demand in the spring. Best case is the nitrogen cycle continues and the bacteria converts the ammonia to nitrite and then nitrate, rendering it mostly harmless.

I do replace some water every year but not usually more than 20% so I feel like there would still be some cya but it never shows up. Idk, just one of those things I guess.

OK - would probably work then, if you get it dialed in. Frequent testing to make sure you don't overshoot on the acid.

We have to drain out pipes for the winter for fear of freezing here

Any thoughts to diluting the 5 gallons of muriatic in 10 gallons of water to create a longer run time on the stenner?