CYA in Trichlor?

[jhm]

I know trichlor is stabilized, but does it actually contain cya? It doesn't list it as an ingredient, and if not, why does it contribute to higher cya numbers over time?

[giroup01]

Trichlor is basically CYA with three chlorine molecules attached to the three nitrogen atoms of the CYA molecule (hence the tri- in trichlor).

In water the chlorine detaches and does its work, and you're left with just the CYA molecule.

That's the simple explanation.

[jhm]

That's the simple explanation.

That's actually a great explanation, thank you. So a friend has been feeding his vinyl pool trichlor for years. His CYA is over 100. I've told him to keep his chlorine high, but to only use bleach. Will this damage his liner (I have a plaster pool so I don't know)? How long will it take to get it down to more reasonable levels?

Thanks!

[Watermom]

Only way to lower is to do a partial drain and refill. No more trichlor or dichlor for this pool.

[aylad]

Using the bleach won't damage the liner, especially with CYAso high. Low pH, on the other hand, can do a number on a liner. In addition to raising CYA, trichlor also lowers pH. Might want to check on that....

Janet

[chem geek]

Just make sure that when the bleach (or any concentrated chemical) is added to the pool, it is added slowly over a return flow with the pump running, preferably at the deep end. For extra safety (especially if this is a vinyl pool with no floor drain or if circulation is poor), lightly brush the side and bottom of the pool where you added the chlorine to ensure thorough mixing.

Bleach is fine when thoroughly mixed, but it is denser than water when concentrated so could settle to the bottom of the pool if you dump it in quickly in one spot without circulation/mixing.

[jhm]

Thanks! Lots of great advice as usual. I've already got him drinking the BBB kool aid. :)

[jhm]

So my friend brought in his water for me to test today. CYA was way over 100. His FC was about 4. He claims his water is clear and algae free. Does he need to drain now, or just keep the chlorine at a higher level? Seems way out of wack.

Also, does the CYA evaporate with the water? He lives in a really hot location (almost desert), so there is a fair amount of evaporation.

Thanks!

[CarlD]

Does he also have a '70 Cadillac Fleetwood he claims gets 75 mpg?

Seriously, if he checks his FC multiple times a day and is constantly adjusting, or has and SWG it may be true, but he's clearly pushing his luck.

Sunshine and evaporation don't reduce CYA--dilution does.

[jhm]

That's what I thought. He'd not happy since he has to have the pool water trucked in. He's buying into the BBB approach though, which is a good thing.

So you think if he keeps FC around 8-10 he should be OK until he dilutes it?

[Watermom]

He can run high cl levels to compensate for the high cya (but he'll have to be extremely diligent about keeping the cl level between 8-15 ALL the time) or he can do a partial drain. Either way will work. If it were me, I'd do a partial drain, though.

EDIT -- as soon as I posted, I saw that you had also posted while I was typing. If he doesn't want to drain, it's ok. But, he MUST not let cl drop below 8 ever or he is gonna have big algae problems. Hope this helps.

[docsobeck]

i've had some experience with high CYA before learning the BBB approach. if it were me, i'd do partial drain as well, but water around here is among the cheapest in the midwest, so it wouldn't cost me more than 20 bucks. if i had to have the water trucked in, i would try to ride it out. assuming that the pool gets used a decent amount, the water will slowly go down due to splash out and backwashing. (if he has dogs, the splash out will be significant. obviously i have experience in that area. : )

anyhow, he'll have to keep the FC level pretty high, but on the other hand with all that CYA he won't be losing much to sunlight, so it's not like it will take a TON more chlorine to keep it high. that's the way i would go.