I've got algae and high CYA -- what should I do?

I've had my inground pool for about a year now and have been doing pretty well this season but came up with a problem so i went to a local pool store and got some advice and now i've come here to get some different advice
and see if you all can help me with any pool problems that come up!


Last week we were getting a lot of rain so I never bothered with the pool and didn't realize my chlorine feeder was out of tablets so the chlorine fell to zero so I just threw in a few more 3" tablets and thought it'd be ok. I check the
chlorine the next day and its still zero then I turn the chlorine feeder up and a couple hours later still zero.

Then I realized there was a tiny bit of algae so I put in an initial dose of algaecide and still no chlorine the next day. I took a water sample to a pool store today and here are the results:

TDS: 600
CYA: 120
Tot. Chlorine: 0.6
Free Chlorine: 0
pH: 7.3
Tot. Alkalinity: 107
Tot. Hardness: 236

I was told the algae and bacteria were taking away all the chlorine so I was told to put in 15 gallons of shock which I did and now the FC is super high finally. Then I started reading on the forums today that with a higher CYA level you need to maintain a high FC level is this true? according to the best guess chart which I took a look at its between 8-12 FC for my CYA level.

All season I've been maintaining around 3 ppm for my FC level, does this mean it hasn't been very sanitary? If so should I flush some water to drop my CYA between 30-50 and maintain a 1-3 ppm or should I keep it how it is and maintain a 8-12 FC reading??

All comments appreciated!!

membership updated.

Kevin, I haven't ever had someone register with a leading hyphen in their user name before, but it turns out that that causes some problems. So, I will change your user name to "KevinV", once I finish this post. Your password (which I don't know) should remain unchanged.

1. If you'll read the Best Guess page, linked in my blue signature block it will explain more.

2. Before you consider draining, you need to be SURE you can do so safely. Vinyl pools can't usually be drained, but when the ground is really wet (as it is in many parts of the country) NO pool can be safely drained, unless it's on a hillside. Even concrete pools can float out of the ground.

3. You want to avoid using any algaecides. Polyquat (www.poolsolutions.com/polyquat.html) is the only algaecide we ever recommend. Some of the others cause real problems, and even polyquat doesn't coexist really well with high levels of chlorine.

4. For now, high levels of chlorine are your only option. You *may* be able to safely do a partial drain and refill, but meanwhile, you need high chlorine. Get a cheap OTO / phenol red test kit, and maintain at least a DARK YELLOW OTO reading.

5. In pools, if the water is clear, the main sanitation issue is person-to-person. That is, somebody who has something gets in the pool and leaves a bit of stuff behind, that carries the whatever to the next person, and infects them. That's a BIG risk in commercial pools, but it's a much smaller one in home pools.

So, to answer your question about sanitation: if your pool were being used by the entire neighborhood, then it probably hasn't been very sanitary with CYA > 100 ppm and FC -> 1-3 ppm. But if it's just been your family, it's probably fine, so long as the water was clear.

6. We say this so much, I feel like a broken record (and yes, I'm old enough to know EXACTLY how a broken record sounds!), but with high CYA, having a K2006 is pretty much a necessity. There's a link in my signature block that will take you to a page with more info and links to Amazon.

Best wishes.