Raising CYA level

[PeterDM]

I have been waiting for my test kit refills to arrive from the US (I used up the last drop of the 0013 as well as the R-0600 & R-0014 at the end of last year). My CYA is not registering at all. It had been low (20 -30) for the last couple of seasons after several years of only using liquid chlorine, so not altogether surprising. I have some stabilizer tabs & have put two in the pool in a couple of socks. How long will this method take to elevate the CYA? Should I buy some granulated cyanuric acid to add? Should I consider buying some stabilized chlorine granules to shock the pool to raise the CYA levels?

Thanks!

 

[Donldson]

Could you post up what these stabilizer tablets are made of? I'm not familiar with such a product.

 

[PeterDM]

The product is brand name Aqua (a Canadian company that supplies many pool products) "Stab Tabs". The composition is listed as 98.5% cyanuric acid, 1.5% "inert ingredients". It recommends one 200 gm puck per 9,000 litres to raise the stabilizer level by 20 ppm. What I am not sure about, is how long the pucks will take to dissolve & become effective. I fairly urgently need to get the CYA to a reasonable level in order to effectively SLAM the pool.

My current readings:
FC 0.5
CC 0.5
TC 1
CH 150
TA 80
CYA less than 20
PH 7.5

 

[Donldson]

Interesting, and looks perfectly fine. The inert is probably just something to help it compress in to a puck.

Since CYA is a fairly weak acid (unlike trichlor pucks) it's probably safe to put them in the skimmer where they will dissolve faster. Once dissolved the CYA is in the water and effecting the chemistry.

If you want fast CYA I personally am a fan of dichlor powder. It adds essentially the same amount of CYA as chlorine and dissolves very quickly. It's more acidic than straight CYA, but with a TA of 80 it shouldn't hurt anything. Adding 10 ppm of FC with dichlor will give you an instant 9 ppm CYA, so you can see how over a couple of days you can get your CYA up quickly while maintaining the chlorine level. Something to consider, otherwise those tabs will add the CYA but like you I don't know how quickly.

 

[PeterDM]

So, you think it's OK to add the pucks directly to the skimmer? They're dangling over the pool jets right now, but I imagine they would dissolve faster in the skimmer. I have 4 pucks in the pool right now, which should raise the CYA (40,000 litres pool volume) by 20 ppm. That should leave me somewhere between 20 & 40 for the CYA level, depending what the exact level is now (the CYA tube was full & the black dot still clearly visible). As I have the pucks, I may as well use them.

I already shocked the pool with liquid chlorine when I opened it a couple of days ago. I was a bit taken aback by how low the FC levels were already when I tested this morning (after picking up my TF100 refills) - presumably that is partly because the CYA level is so low. Now that I have my test kit operational I can focus on slamming the pool. I'll report back on how quickly the stabilizer pucks dissolve.

 

[Donldson]

So, you think it's OK to add the pucks directly to the skimmer?

These stabilizer pucks specifically: yes I think it will be ok. They are much less acidic than trichlor and shouldn't cause the issues a typical chlorine puck would. This is assuming you keep your pump running the entire time.

 

[PeterDM]

FWIW: the pucks dissolve very slowly. So, I ended up grinding them up & distributing the resulting granules into the pool.

After 2 pucks the CYA recorded was up to about 20, which seems about right. Ground up another two pucks which should get it to around 30 plus. I'll see where to go after that.

 

[mknauss]

Do not dump stabilizer directly into the pool. It will stain your liner.

 

[PeterDM]

I ground it up fine before using it, sprinkled it over the surface & then swirled it around with the pool brush until it dissolved.

 

[PeterDM]

Actually ... sticking it in a sock created more problems. My ground up stabilizer was (I assume) much finer than granulated stabilizer. As soon as I put it in the sock & tried to put it in the pool, it wound up on the (white) pool capping. Yes ... it stains! Not a major problem.

Bottom line: these stabilizer tabs are not a very practical way of adding stabilizer to the water - they dissolve extremely slowly which means if you are in any kind of hurry to raise the stabilizer from very low levels, they are not very useful. As I now have the stabilizer at around 25, I'll dissolve a couple more tabs over the next few days & see where I end up.