Chemicals for IG Indoor Plaster Lap Pool

Jul 30, 2012
21
Sandpoint, ID
#1
We purchased a house in November with an indoor in-ground plaster 10x60 lap pool ~16k gallons. Pool is ~25 years old and looks like original plaster. Pool room does have windows along one wall, but doesn't get very much sun hitting the water. I'm just looking for a sanity check from the experts here before I start dumping stuff in the pool. :D

The pool was winterized by the previous owner (water level lowered, returns blown out and plugs inserted, filter drained and some pool antifreeze added in some pipes, some "winter chemicals" added and water level re-added to just below the tile). No idea what they added for "winter" chemicals but the water is clear. There were various pool store products left with the pool, including algicides. Yuck. But there was also an old Taylor test kit, so that's a good sign. This is my second pool, but my last one was outdoor in sunny California which is quite different compared to an indoor pool in North Idaho. I'm planning on using liquid for chemicals, so bleach and muriatic acid. I work from home, so it's easy for me to add when needed.

I've successfully opened the pool (removed plugs, added water, brushed, vacuumed and backwashed). Flow meter shows 32 GPM so I have the pump set to run 8 hours a day. Never used a sand filter before, had a cartridge system with the last pool. Pressure in the sand filter was ~5 before I vacuumed and ~20 after, and the flow rate had dropped to ~15 GPM, a quick couple minute backflush and I was back to 5 on the filter and 32 on the flow meter. I have not added any chemicals yet. We have started to have a few warmer days (over 55 degrees in the pool room), so I have turned on the heat pump and the pool has gone from 42 to 52 so far. :cool:

Here are my numbers with a fresh TF-100 test kit that arrived yesterday:
FC 6
CC < .5
PH 7.5
TA 90
CH 210
CYA < 20

All in all not a bad place to start. I was looking at PoolMath and my pool currently has a CSI of -0.35 "Potential to become corrosive to plaster".

First thing I plan to do is add some calcium chloride to get the CH up to ~300. CSI would be -.22 at current temps, and 0.08 at 85 degrees. Sound good?

Then, I'm considering adding some stabilizer, in small quantities and waiting a week to re-test until I get CYA up to ~20 since this is an indoor pool. Or maybe I'll just leave it as-is and try it out first. It did register when I tested CYA, but I could still see the spot with the liquid past 20.

Thought about raising TA a little, maybe as high as 120, but I may just leave it as-is and try it at 90 first.

So I think my goal is:
FC 3-4
CC 0
PH 7.5
TA 90
CH 300
CYA 20

Does that make sense? Anything else I should be considering? First indoor pool and we sure are looking forward to it getting warm enough to jump in!!! :)

Best Regards,
James
 

pooldv

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TFP Expert
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Aug 10, 2012
25,006
DFW, TX
#2
Numbers aren't bad. Pool looks good! Yes, looks like a good plan. I would take cya up to 30. It is easier to measure and know for sure. There is no downside to CYA at 30 vs 20. No need to raise TA at all, 70-90 is your target.

More here, Pool School - Recommended Levels
 
OP
OP
J
Jul 30, 2012
21
Sandpoint, ID
#3
Numbers aren't bad. Pool looks good! Yes, looks like a good plan. I would take cya up to 30. It is easier to measure and know for sure. There is no downside to CYA at 30 vs 20. No need to raise TA at all, 70-90 is your target.

More here, Pool School - Recommended Levels
Thanks for the quick response and advice! I did read the Pool School Recommended Levels, but since it is an indoor pool I wasn't sure what to adjust from those numbers. I'll leave TA at 90 and shoot for a CYA between 20-30. I don't know yet how often or how much bleach I am going to need to add to keep FC at 3-4. Sometimes I travel, and I may use tabs if the pool needs it for that so I'll get a small amount of stabilizer from those over time. I'm hoping that since it's indoor with little sun, I can just add some extra bleach and call it good for a week. We'll see!
 

pooldv

Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
25,006
DFW, TX
#4
Yes, those numbers will work fine for indoor as well. The only thing that changes is a lower CYA number because there is no sun on the pool. When you need to leave the pool alone for a while or even know you aren't going to swim and don't want to mess with it for a while you can raise FC up to shock level for your CYA, [FC/CYA][/FC/CYA]. Try that and see how long it takes for FC to drop. It is safe to swim with FC up to shock level for your CYA. Floating pucks is also fine just keep track of the CYA.