Large CYA drop over winter?

[MJuric]

Last fall I tested CYA and it came in at over near or over 100. Just tested to start getting ready to open and I have a CYA of...well near zero. I filled the tube to the top and could still easily see the dot. We've had a significant amount of rain as the pool is near the top at this point and needs some drained out. I'm just wondering if such a significant drop normal over winter or is it possible my reagent is bad, less then a year old purchased last Aug or so.

Thanks

Matt

 

[Self Evident]

You will experience some CYA loss over the winter. how much depends on ... ummm.. I don't know. But, for example, over this past winter, from early October thru late March, my CYA dropped from 40 to much less than 20 (not zero, but no where near 20).

Now, I opened to a clear & clean pool. Was your pool likewise, or was it a bit on the green side? As an other example- last year, I opened to a swamp and had a true zero CYA. Now, I don't know what it was at the end of the prior season, but, at that point, this pool had been chlorinated almost exclusively by pucks, so it's CYA was probably very high. Until I stopped caring for it at all from Sep '15 thru Jul '16.

Another consideration is that when you took your water sample, had you ran the pump to mix the water first? If not, you may have tested a mostly rain water sample. Just a thought...

 

[duraleigh]

I doubt the reagent is bad, We have reasonably common reports of CYA loss over the winter......yours is pretty drastic.

It actually brings up another issue.....ammonia.

Get your pump and everything up and running. Put in enough liquid chlorine to get to say, 10 ppm. Now check it in about 15 minutes. If the FC is gone or almost gone, your CYA converted to ammonia.

Let us know if that happens and we'll tell you how to get it out (easy).

 

[JayG]

In the northeast although we had a lot of precipitation over the winter my CYA went from 65 to ~10....more of a drop than I expected. I added dichlor to both add FC and add CYA. My CYA is now 50 and FC has been relatively stable since that addition, so I don't think ammonia is/was our problem. This is only my second season in our pool, so I'm new to this. I thought I'd just add a data point.

 

[MJuric]

Now, I opened to a clear & clean pool. Was your pool likewise, or was it a bit on the green side?

Another consideration is that when you took your water sample, had you ran the pump to mix the water first? If not, you may have tested a mostly rain water sample. Just a thought...

This is an interesting point that may be exactly the case. We got a lot of rain plus the snow over winter so there's no way to get down to where "Last years" water might be. Also I do have some green but there is a pretty clear dividing line as to where it starts and stops...and it's all toward the top. I could have layers of water, old pool water down below and rain water above.

I have a new multi port coming in today and will get that installed, pump running etc and test again to see if once mixed I get higher numbers.

Thanks.

- - - Updated - - -

I doubt the reagent is bad, We have reasonably common reports of CYA loss over the winter......yours is pretty drastic.

It actually brings up another issue.....ammonia.

Get your pump and everything up and running. Put in enough liquid chlorine to get to say, 10 ppm. Now check it in about 15 minutes. If the FC is gone or almost gone, your CYA converted to ammonia.

Let us know if that happens and we'll tell you how to get it out (easy).

I will do both of the above once I have the pump running. I will clear out some of the larger gunk, get the pump running and let it run for a while to mix things up and then test. If the CYA jumps up I know I had layered water. If it doesn't I will do your test.

Thanks,

Matt

 

[duraleigh]

I will do both of the above once I have the pump running. I will clear out some of the larger gunk, get the pump running and let it run for a while to mix things up and then test. If the CYA jumps up I know I had layered water. If it doesn't I will do your test.

Good plan!

 

[dd564]

Just a CYA question in general.
Is it expected that CYA would vary much during the season.

To me it seems like once you get it to a certain level it would stay pretty established during the year if there is outside water being added to the pool.

Is this an accurate assumption or am I wrong?

 

[pooldv]

Cya drops 3-5 ppm per month on average.