CYA from 30 to 100

[JoeRJGR]

Hey guys,

I just started using the TFP method this year...when I started the pool up I was unable to get a FC reading and the CYA level was 0. Actually every time I open the pool the CYA is at 0. Chem Geek surmised that I had some bacteria and/or algae that grew over the winter and reduced the CYA. I solved this problem by slamming and have had no issues this summer....but here's where it gets interesting....

The Taylor test kit I bought had very little CYA reagent in it so I ran out at least a month ago. (We go away a lot and I travel during the week so there is no way I can not use Chlor tabs.) Since Leslies uses the Taylor CYA test I figured I would just have them do that test only until I ordered more reagent in the spring. For the last 6 weeks they have told me that my CYA level was at 30. I had a bit of an algae bloom a week ago even with the FrChl at 7.0!

I ordered new reagents early and tested myself for CYA. I'm a 100. Took it to Leslies, they confirmed 100 (different kid). I mixed 1/2 pool water and 1/2 tap water to make sure that the level wasn't higher than 100, and it is not.

I know everyone says that CYA stays in the pool all winter, but that has never been the case for me. So I'm wondering if I can close with the CYA this high assuming it will drop over the winter. My concern is that if something grows again it will have more CYA to consume and a bigger mess for me next summer. I'm going to wait till next week to close because here in jersey it will by 85 degrees for the next few days and I don't want to cover it when its that warm.

Thoughts? anyone else loose their CYA over the winter? My plan was to keep the FrChl at about a 10, Add some Polyquat, and close.

Thanks

 

[pinguy]

Don't trust pool store tests .. they are very often inaccurate.

How much CYA did you add? It can take several weeks for it to dissolve and register on the test - I'm assuming that is why yours jumped so quickly.

CYA isn't consumed by algea/bacteria. Some people's CYA levels lower over the winter, others don't. Since you have a mesh cover, your CYA level probably goes down due to dilution.

In any case, wait until your water temp is below 60 to close - algae isn't going to grow at that temperature.

 

[tim5055]

Well, You seem to have verified that your CYA is somewhere between 100 - 200. If the pool is clear you want to keep it that way. Let's call the CYA 200 so your MINIMUM FC level should be 14 at all times.

I agree that you should wait until the water is below 60 to close. While algae can grow in cold water, it's growth rate is reduced the colder the water gets. We recommend closing below 60 and re opening before it gets above 60.

There is a bacteria that consumes algae and it is what the CYA reducing product on the market is based on. The problem is, that the conditions that allow this bacteria to thrive and do it's work are still an unknown. That is why the commercial product is reported to be hit and miss as to when and who it works for. You seem to have found the version of this bacteria in the wild as you report your pool has gone to zero before.

So, wait until below 60 to close. Keep the pump running and chlorine at 14 or more until then. When you close a quat based algecide can help keep the algae away. Re-open before the water reaches 60 and I would hope it is nice and clear.

 

[JoeRJGR]

Never added CY, just came from pucks....have a hard cover...

 

[pooldv]

There is bacteria that can consume cya that sometimes occurs when FC levels drop to 0 or close to 0. No harm in closing with high cya and see what it is when you open.

 

[chem geek]

If you let the pool go over the winter then there are basically three things that could happen with regard to CYA. It could go down some from water dilution. It could go down a lot from bacterial conversion resulting in ammonia creating a huge chlorine demand upon opening. Or it could go down a lot from bacterial conversion resulting in nitrogen gas in which case you don't have a significant chlorine demand.

The worst case is that you lose all 100 ppm CYA that gets turned into ammonia requiring 250 ppm FC to get rid of it. Let's hope that doesn't happen.

 

[Swampwoman]

Okay, madcap question...why not do a partial drain now to reduce the cya, use TFP closing techniques, open clean and switch to liquid chlorine next season?

The cost and effort of this plan is, IMHO, less cost and effort than a Herculean ammonia fight come spring, methinks

 

[440dodge440]

The worst case is that you lose all 100 ppm CYA that gets turned into ammonia requiring 250 ppm FC to get rid of it. Let's hope that doesn't happen.

Is this 2.5:1 ratio of FC to CYA turned to ammonia valid regardless of CYA level? I ask because this happened to me and I've been curious as to what the CYA level was at close (I didn't own the house when the pool was closed)

 

[tim5055]

Is this 2.5:1 ratio of FC to CYA turned to ammonia valid regardless of CYA level? I ask because this happened to me and I've been curious as to what the CYA level was at close (I didn't own the house when the pool was closed)

From Chem Geek's previous post I would say yes, but there is a big unknown - CYA does not always end up as ammonia in the pool. Many times (maybe most times) the conversion completes the full cycle and ends up as Nitrogen Gas which dissipates. It would look like CYA - TO - AMMONIA - TO - NITROGEN GAS

But, we seem to be drifting from the OP's question

 

[JVTrain]

As has been said, you can lose CYA over the winter. The risk when you close is that the FC drops to 0 before you open in the spring. When you have no FC in the pool, that's when you can have the possibility of a bacterial CYA to ammonia conversion. As has also been said, this conversion can proceed all the way to ammonia being fully oxidized and outgassing as nitrogen. You could have all of your CYA converted to ammonia and very little that outgasses as nitrogen. You could have all of it outgas as nitrogen. That means you could have 0 CYA, 100 ppm ammonia in the spring. You could also have 0 CYA, 0 ppm ammonia in the spring or anywhere in between.

To increase your chances of avoiding this problem entirely:
1. Close late - water temp below 60 degrees for at least several days, all day.
2. Bring your FC up to SLAM recommended levels for your measured CYA immediately before closing. Consider using a correct dose of Poylquat 60 as well.
3. Close cleanly with as little debris in the pool as possible
4. Cover the pool.
5. Open early in the spring. Before temps are above 60 degrees.

The idea is to have some FC remaining in the pool when you open in the spring. If you can do that, there's very little chance of this CYA/ammonia conversion taking place.

 

[JoeRJGR]

Thanks Guys

My plan is pretty much exactly what JV mentioned. I have never had any FC upon opening in the 7 years I have had this pool. However, I also never closed it with 14 ppm FC, and also never waited till the water temperature is 60 or below. We'll see what happens....

Oh and by the way, many people suggest I just use bleach instead of the Chlor tabs....I would love to, but Im not home during the week very often as a I travel and just about every other weekend we're away..

 

[ping]

Thanks Guys


Oh and by the way, many people suggest I just use bleach instead of the Chlor tabs....I would love to, but Im not home during the week very often as a I travel and just about every other weekend we're away..

You have three options.
1. Switch to SWG.
2. Add an automated liquid chlorine injection system such as a Stenner pump.
3. Keep it as is and figure you need to drain some every year. You know the FC/CYA relationship and that is what matters. Hopefully following JV's suggestions will make it much easier for you in the spring.

 

[Agent99]

The Liquidator is another auto chlorine injection system that can allow one to go ~1-2 weeks before needing to add chlorine. It all depends on the amount of liquid chlorine, the strength of the liquid chlorine, and how much FC you lose per day, how long you run the pump, etc.

 

[JoeRJGR]

Ping,

I have thought about a SWG just since we're not home a lot....also, the unfortunate part of this is I THOUGHT my CYA was 30 because I was trusting the kids at Leslies to accurately read the Taylor kit....had I known that the CYA was creeping up, I could have turned the chlorinator off and then started using bleach. When the CYA gets over 40 ppm I hold it very well. I shocked it 2 weeks ago and I lost maybe 2 ppm free chlorine since then.

Thanks all for the advice.