CYA much too high, algae -- drain/refill or SLAM?

[Ignorant Pool Owner]

The challenge:

Thought I had chemistry under control, but a week away and returned to find crawler hung up on thermometer cord. Bottom of pool covered in green slime. This tells me that I have had an algae bloom, but was simply vacuuming it up. Need to kill this stuff off for good.

Challenge: 45,000 gallon pool, CYA is probably north of 150 (scale on test kit tube doesn't go that high; my best guess). SLAMming would require enormous amounts of chlorine (25 gallons at 11% concentration at current CYA levels); perhaps too much. Ideally I would drain and refill, but we're in the middle of a drought here in northern CA and such things, while not yet prohibited, are not encouraged. Further, if I drain and refill, I do not know how to eliminate whatever algae might be in the cartridge, or how to kill whatever is left stuck on the pool walls.

So: SLAM or drain/refill and deal with the walls and cartridge? Any and all suggestions appreciated; I'm a rookie pool owner. Many thanks.
--
Mark

 

[JasonLion]

Welcome to TFP!

Drain and refill is by far the better option if it is at all possible. You will still have to fight algae once the pool is refilled, but doing so will be much much simpler. You probably don't need to do a 100% drain and refill, draining 75% is probably enough.

You might want to do a CYA test with dilution to get a better handle on just how high your CYA level really is. To do this, mix equal parts of pool water and tap water, do the CYA test normally with that mixture, and then multiply the result by two. You lose a lot of precision that way, but it will tell you if the level is 100, 150, or 200+.

 

[Ignorant Pool Owner]

Jason:

Many thanks for the quick response

Welcome to TFP!

Drain and refill is by far the better option if it is at all possible. You will still have to fight algae once the pool is refilled, but doing so will be much much simpler. You probably don't need to do a 100% drain and refill, draining 75% is probably enough.

I'm leaning this way. But if I drain and refill, do I have to do anything to any algae that might be on stairs/walls or in the cartridge?

You might want to do a CYA test with dilution to get a better handle on just how high your CYA level really is. To do this, mix equal parts of pool water and tap water, do the CYA test normally with that mixture, and then multiply the result by two. You lose a lot of precision that way, but it will tell you if the level is 100, 150, or 200+.

I'll give this a try. I might also do a CYA test on the tap water just to get a baseline number, as that's what will go in the pool.

With the current drought, I'm sure my neighbors will not be happy with me. But it's getting to the point where I can't put enough chlorine in to keep things sanitized.

 

[Kiss4aFrog]

Welcome to the forum

Drain, refill and then SLAM to get rid of the algae. http://www.troublefreepool.com/content/125-slam-shock-level-and-maintain-shockingl

There shouldn't be any CYA in your tap water.

 

[Ignorant Pool Owner]

Drain, refill and then SLAM to get rid of the algae.

Once the pool is drained, should I not try to clean off algae from steps, etc.? Should I try to "shock" the cartridge before refilling the pool?

 

[Kiss4aFrog]

It never hurts to get everything done as early as you can. While draining or filling thoroughly clean the steps or ladders, if you have a light the light and niche and pulling the cartridge and cleaning it are always good ideas.
You don't need to shock the cartridge just a good cleaning as when you SLAM (shock) the pool you will be running more than enough chlorine through everything !!