New (old) house, new (old) pool, test numbers are confusing

[Bryan]

Took a water sample to the pool store today (since I left my TF-100 test kit at the old house ), here are the results:
FC 0.0
pH 8.0
TA 125
CH 450
CYA 100

Water is clear, and I've been chlorinating with liquid chlorine for the last few weeks to get rid of the algae that was there. I put 1/2 gallon of 10% in on Sunday, and here it is Wednesday and FC is at 0. The nice person at the pool store says it's because I'm not using stabilized chlorine, aka pucks. :? But if my CYA is 100, why in the world would I want to introduce more CYA by using pucks?? I have added acid to bring the pH down, will recheck in the morning, but what's the concensus regarding the FC/CYA?

Thanks everyone!

Bryan

P.S. The high CH is maybe due to the marcite erosion?? It doesn't look too good, but I'm hoping to get at least a year out of it before I have to refinish.

 

[257WbyMag]

Re: New (old) house, new (old) pool, test numbers are confus

Algae consumes FC really quickly. If you put 10% in on Sunday, it was probably gone by Sunday evening.

If your CYA is 100 (or more), it's going to be tough for you to fight algae because the amount of FC that it would take to be effective is substantial. You would be best served by changing out water to reduce your CYA to around 50 or so before doing much else.

Your pH is high. You essentially want that between 7.2 and 7.8.

Your CH could be high from the marcite. It could also be high from cal-hypo additions and also from your fill water. Have you checked the fill water CH to see where that is? Might surprise you.

So, lower your CYA and you can go from there.

 

[Bryan]

Re: New (old) house, new (old) pool, test numbers are confus

I haven't checked the fill water because I haven't put any new water in. I also haven't discovered a drain where I can purge pool water, maybe they don't have those here in Florida LOL! What's the best way to change out water? With my old pool (in Oklahoma) I just pumped it into the sewer drain line from the house, but Darn if I can't find one here. Also, I don't know if the previous owner used cal-hypo; I do know they used 10% liquid. As for the algae, it's been visibly gone for over a week now.

Thanks!

 

[257WbyMag]

Re: New (old) house, new (old) pool, test numbers are confus

Maybe you haven't added any water, but the previous owners have. It's doubtful that your fill water has high CH down there in FL, but that is one of the things worth checking in the future. You can deal with CH later though. Right now, you need to get your CYA and FC issues under control.

If you don't have the ability to drain directly from the pool, then you can rent a pump to drain it. As long as you are on sewer and not a septic system, you can route the discharge to the sewer clean-out on the outside of your house. This is how I have done mine in the past.

You may not see algae, but just because you don't see any doesn't mean that it is all gone. With an FC of zero, I would suspect some still being present. The way to tell is to do an overnight FC loss test. Raise the FC to a certain point after the sun is down and then check it again in the morning before the sun comes up. If the morning FC is within 0.5 ppm of the previous evening's FC, it's safe to assume that your algae is gone.

One more thing about draining pools, especially there in FL, has to do with water table issues. If your water table is high, draining a pool can result in your floating the pool. I would drain probably no more than a foot at a time, refill, retest, and repeat as needed until your CYA is where it needs to be. This is a slower way to change out water, but it is safer when high water table concerns are present.

 

[Bryan]

Re: New (old) house, new (old) pool, test numbers are confus

Thanks for the tips! I'll have to try the FC loss test tomorrow night, assuming it quits raining before then. And thank you...sewer clean-out, that's what it's called. Don't know why I couldn't remember that. But the funny thing is, I can't find it! Like I said, maybe they just do things different down here in F-L-A ???

As for the water table issue, I was wondering about that when they said they completely drain the pool for about three days when they resurface it. I don't know how shallow it is; I'm about a quarter mile from the river and 3 miles from the coast, so I assume it's not very far down.

And here's a stupid question: why is there no way to lower CYA without replacing water? Is it just chemically impossible to "de-stabilize" water? Again, thanks very much!

 

[257WbyMag]

Re: New (old) house, new (old) pool, test numbers are confus

And here's a stupid question: why is there no way to lower CYA without replacing water? Is it just chemically impossible to "de-stabilize" water? Again, thanks very much!

Not a stupid question at all. You actually can reduce CYA without changing out water by using a reverse osmosis service. This is a service though that is not available in all areas and is also fairly expensive. Most of the time, people use R/O services to lower CH in areas where the fill water is very hard and water is at a premium. This means places like AZ, NV, and parts of CA. Anyway, it is usually cheaper and easier to simply change out water. But no, there is no product that you can add to neutralize CYA. Like metals, the most readily available way to get rid of it is to drain it off and start anew.