New member, high CYA, what to do?

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J

jamescookmd

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Bronze Supporter
Apr 10, 2018
11
San Jose, CA
2 year pool owner, occasional forum reader, first-time poster -- hello everyone!

I've got a CYA of ~150 and I'm wondering if I need to partially drain my pool, do reverse osmosis, or do nothing.

A couple days ago I did a full set of chemistry tests for the first time in a year. I test TC and pH weekly, but got lazy. :) I got these results:

TC 2
pH 7.5
TA 120
CYA >100
Calcium hardness 650

I use a Taylor K-2005 kit, less than 6 months old. My calcium hardness was 480 a year ago according to my log book. I don't have historical CYA levels.

I took a sample to Leslie's Pool today and they got FC >5, TC >5, CH 380, CYA >100, TA 90, pH 7.5, Cu 0, Fe 0, TDS 1000, phosphates 2500. Of course they sold me some PhosFree, which I've since learned isn't that useful, and I can't return. I forgot we don't trust pool stores. Whoops. :p

After reading the forums here I re-measured my CYA with dilution and got 120-150 (it's hard to know exactly when the dot disappears).

The pool is 2 years old. I've been using trichlor tablets for maintenance, and shocking with dichlor occasionally, which is probably where all the CYA came from.

My water is clear. I had some algae last year, but haven't had any algae this year.

Should I do anything? Partially drain? Reverse osmosis? Just wait to see if I get algae?

Any advice appreciated, oh masters of pool wisdom,

James
 
Hey neighbor,
the first thing you should do is upgrade your test kit. The K2005 is fine EXCEPT it doesn't have the FAS-DPD chlorine test. It uses the OTO test which doesn't go very high. If you ever get algae again and need to SLAM your pool to get it clear, your need the better chlorine test. You can buy it separately by itself and you should be good to go. With your CYA as high as it is, I would definitely drain at least 60-75% of your water and refill. After the refill, check your CYA again and hopefully it's down to a manageable level. I keep mine at 50 so the sun doesn't burn the chlorine off so fast. Even at 60 you should be just fine. You will also lower your CH some with the drain and refill, depending on your refill water.

From there, I would add enough liquid chlorine or bleach to get your FC up to the right level. That will depend on your CYA. I run mine in the 6-8 range and never below 4 with my CYA at 50. You are currently in danger of getting algae with your FC at only 2 and with such a high CYA. Keep a close eye on that relationship. That is the #1 fundamental principle of TFPC. Also, don't use anymore chlorine tablets or powdered shock to chlorinate your pool. Stick to only liquid chlorine or bleach. All those solid forms of chlorine add either CYA or Calcium to your pool. That's how your numbers got to where they are in the first place.

I had similar issues a couple of years ago. I had a pool guy that used nothing but trichlor pucks. I fired him and took over the pool myself with a CYA of 200 and a CH of over 1100. I did a full drain and refill and basically started from scratch and my pool has been sparkly ever since.
 
You can run high cya, but you are going to need a few things. Going forward it's tfpc and liquid clorine regardless.

Firstly, upgrade your k2005 with the fas-dpd kit. You need a good diluted cya test. Manage your pH when it hits 9 fc, you will have to let your fc drft down to this probably once a week. Keep your fc high enough rest of the time according to the fc/cya chart, if 150 cya is not on the chart I believe it's 7.5% cya. If you have a problem with the pool dump 50-75% water and refill. After or or two years the cya will come into spec.

Or you can dump the water now.
 
Thanks for the advice! I'll definitely upgrade my test kit. It sounds like draining would fix my CYA and help with CH, so that sounds good.

Any advice on draining a pool? I didn't see anything in Pool School. Rent a submersible pump? Where? Is my water OK to go on a lawn, in a storm drain, or only down a sewer clean-out?

Thanks again,

James
 
You have a couple options - backwash to waste from your main drain(s) or get a submersible pump from a local hardware store, Harbor Freight, etc. Whichever works best for you. Effects on grass vary, so I can't give you any promises on that one. Most probably feel it's okay, but every once in a while it seems to not do well.
 
You will want to drop you CYA if it is above 100. I would suggest further testing to determine how high your CYA actually is by diluting the sample 50/50 with tap water as this will determine how much water minimum to replace. If you can backwash to drain do that. If you have a large yard then you can utilize much of the water for irrigation. If you do not have these options then I suggest you contact your city officials about draining your pool. Here we have to submit an application for approval before the process and the application actually asks about the CYA level of the water, imagine that. We also need to contact flood control prior to the scheduled drain day and it is smart to give your neighbors a heads up as well. Home depot rents a submersible or the larger suction pump and all the hoses you need.

Plan this process as you can solve several problems and tackle upgrades during the draining.
 
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