Best method to raise CYA

Cbed1013 · May 18, 2017

I just re-filled my pool this season and am struggling to get my CYA up. I have been using dichlor shock (3 pounds added so far) and trichlor tabs (about 10 tabs dissolved so far). It hasn't been working as my CYA is still below 10. My pool is 25k gallons.

Here are my full test results

FAC - 1
TAC - 1
CYA - <10
TA - 100
PH - 7.8
TDS - 500

I am hesitant to add stabilizer, as in the past my CYA has risen off the charts quite quickly. If I keep on the path of using dichlor shock and trichlor tabs, how much more will I have to add before my CYA gets up around 30? Would I be better off just adding stabilizer?

Thanks!

spinPHD · May 18, 2017

Just add the stabilizer and ditch dichlor and trichlor. You can hang on to the pucks in case you go on vacation or something, but it's a lot easier just to use stabilizer and start using liquid chlorine.

pinguy · May 18, 2017

Any particular reason you need to use solid chlorine over liquid?

In any event, it's going to be difficult to keep your FC up on a sunny day with a CYA <30. I would use poolmath to add enough to get it to at least that level.

It depending on your pool, it will likely reach unmanageably high levels during the season unless you monitor and replace water accordingly.

Cbed1013 · May 18, 2017

Was only using the solid chlorine until I got the stabilizer to the correct level. Then plan on switching to liquid.

I will follow the advice and get some stabilizer to get the cya up and switch over to the liquid.

On a separate note, will Calcium Hypochlorite raise my cya? At the pool store they say no, but I thought anything except Sodium Hypochlorite would?

Thanks!

Fingaling · May 18, 2017

Calcium hypochlorite will not raise cya but will raise calcium hardness

pinguy · May 18, 2017

Cbed1013 said:
Was only using the solid chlorine until I got the stabilizer to the correct level. Then plan on switching to liquid.

I will follow the advice and get some stabilizer to get the cya up and switch over to the liquid.

On a separate note, will Calcium Hypochlorite raise my cya? At the pool store they say no, but I thought anything except Sodium Hypochlorite would?

Thanks!

Cal-hypo raises calcium hardness (CH), which is the other chemical we test for where you can only remove it by replacing water.

High CH can become problematic due to scaling.

wjr75 · May 18, 2017

I have the same 20k size pool and according to pool math a 3" 7oz trichlor tab will add 1.7ppm ppm CYA. I use them early in the season to raise my CYA until I hit 45ppm which is my sweat spot. I think testing for CYA under 20ppm may not be accurate. I didn't look up the dichlor shock addition but you should have added 17ppm CYA using the 10 trichlor 3" pucks unless you have a leak and have been adding water.... Just looked up the dichlor for you which should have added 9.1ppm for 3lbs. You should be around 26ppm CYA according to pool math. If you have a leak and are adding water not due to evaporation that may scew these results.

domct203 · May 19, 2017

Cbed1013 said:
I just re-filled my pool this season and am struggling to get my CYA up. I have been using dichlor shock (3 pounds added so far) and trichlor tabs (about 10 tabs dissolved so far). It hasn't been working as my CYA is still below 10. My pool is 25k gallons.

Here are my full test results

FAC - 1
TAC - 1
CYA - <10
TA - 100
PH - 7.8
TDS - 500

I am hesitant to add stabilizer, as in the past my CYA has risen off the charts quite quickly. If I keep on the path of using dichlor shock and trichlor tabs, how much more will I have to add before my CYA gets up around 30? Would I be better off just adding stabilizer?

Thanks!

3lbs of dichlor will add 7.3ppm of CYA in your 25K gallon pool.

80oz (10-eight oz tabs) of trichlor will add 13ppm of CYA in your 25K gallon pool.

That's a total of 20.3ppm of CYA added. Your original level of <10ppm could have been zero ppm, & 20ppm or less will be hard to read on the test. You should add 10ppm of 100% CYA to the pool using the sock method, retest once it all completely dissolves, and re-dose the 10ppm as needed until you reach your target.

When I add CYA, I don't check until 24 hours after all of it has dissolved. I want to make sure it is completely dissolved so I get a good reading and don't overshoot.