Pool Reset

[birchdale]

Hi everyone,

First time poster, long time lurker.

My pool water (and plaster) is about 9 years old. Current chemistry (per TF-100) is:
FC: 1.5
CC: 0.5
pH: 8.0
TA: 50
CH: 1175
CYA: 10
Temp: 75°F
CSI: 0.66

I have a long list of problems:
- Fair amount of scaling on the tiles and rock waterfall.
- The SWG cell scales up/needs acid cleaning every two weeks, but has been bypassed for the last several months.
- The plaster is sandpapery.
- I constantly have to add liquid acid to bring the pH down.
- Algae spots, mostly dark green, with buildup in the plumbing and inside/outside of the automatic cleaner hose. Surprisingly, the water is clear.

My city water has a CH of 200 and TA of 120.
I have a water softener that can be used to partially or fully fill the pool with.
Weather next week is sunny, 70's and 80's.

I'm planning a full reset starting tomorrow, as follows:
1. Have the tiles and waterfall rocks blasted clean.
2. Drain the pool and have it acid washed.
3. Clean the pool filter.
4. Fill water (using meter to figure out the pool capacity).
5. Use powdered CYA, liquid chlorine, and acid to bring the new water chemistry to the correct levels.
6. Add salt and allow it to dissolve.
7. Install a new SWG cell.
8. Install a new automatic pool cleaner.

My questions are:
1. Does this plan sound reasonable? Did I miss anything?
2. What mix of City/Softened water should I fill the pool with?
3. Any advice on how to get rid of the algae in the plumbing/any spots that may survive the acid wash?

Thank you in advance for your help.
Basil.

 

[PoolGate]

CH is really 1175? CSI is somewhat high as well how long have you been using the tf-100?

 

[birchdale]

CH is really 1175? CSI is somewhat high as well how long have you been using the tf-100?

Yes, CH is very high, in the past as high as 1500. I've had the tf-100 since late 2019. thanks.

 

[DeanP66]

You don't even need to refill from the water softener. You could fully drain and refill from your tap (CH 200) and you'd be at 200 with a complete fill. Then add your CYA and liquid chlorine. Once you get it filled up and the CYA added via sock method, do a SLAM for a day or two. That should clean out all your pipes of any algae residue.

Just be aware that you'll be taking a small layer off the plaster when you acid wash, so if the plaster is questionable to begin with, you may want to skip that. Do you have a lot of staining on the walls and bottom? A couple of pics would help a lot. It may be old iron stains from use all these years. If that is the case, you can skip the acid wash and instead do an Ascorbic acid treatment BEFORE draining to lift the stains into solution. Then when you drain, all that iron (if there is any in there) will leave the pool with the water.

If stains aren't an issue, an acid wash might help some with the calcium deposits on the plaster. My pool had a similarly high CH when I took it over from our pool guy, and I too, did a full drain and acid wash and definitely noticed quite a bit of calcium deposits come off after it was done. It will also lessen over time by keeping your chemicals and especially your CSI on the negative side. Keeping in the -0.5 to -0.3 range will continually help the plaster shed that extra layer of deposits. For months after my acid wash, I would see a lot of loose calcium in the bag of my Polaris 280 cleaner so I knew it was continuing to dissolve.

Beautiful pool, BTW!!!

Also, when you're ready to get a new SWG, make sure you get one rated for at least 40,000 gallons so it doesn't have to work full throttle all the time. It will last longer in theory that way.

 

[birchdale]

You don't even need to refill from the water softener. You could fully drain and refill from your tap (CH 200) and you'd be at 200 with a complete fill. Then add your CYA and liquid chlorine. Once you get it filled up and the CYA added via sock method, do a SLAM for a day or two. That should clean out all your pipes of any algae residue.

Just be aware that you'll be taking a small layer off the plaster when you acid wash, so if the plaster is questionable to begin with, you may want to skip that. Do you have a lot of staining on the walls and bottom? A couple of pics would help a lot. It may be old iron stains from use all these years. If that is the case, you can skip the acid wash and instead do an Ascorbic acid treatment BEFORE draining to lift the stains into solution. Then when you drain, all that iron (if there is any in there) will leave the pool with the water.

If stains aren't an issue, an acid wash might help some with the calcium deposits on the plaster. My pool had a similarly high CH when I took it over from our pool guy, and I too, did a full drain and acid wash and definitely noticed quite a bit of calcium deposits come off after it was done. It will also lessen over time by keeping your chemicals and especially your CSI on the negative side. Keeping in the -0.5 to -0.3 range will continually help the plaster shed that extra layer of deposits. For months after my acid wash, I would see a lot of loose calcium in the bag of my Polaris 280 cleaner so I knew it was continuing to dissolve.

Beautiful pool, BTW!!!

Also, when you're ready to get a new SWG, make sure you get one rated for at least 40,000 gallons so it doesn't have to work full throttle all the time. It will last longer in theory that way.

I appreciate the info and suggestions!
Thankfully there are no stains. I was hoping acid washing would reduce the plaster roughness and clean up any entrenched algae spots.
The plaster is in good condition. The contractor applied generous amounts of it when he re-plastered the pool in 2012, so hopefully it will survive the acid wash.
The replacement cell is a generic T15 cell rated for 45,000 gallons, will try to run it at 55-60% as with the previous cell.

 

[DeanP66]

How long do you run your VSP? I have a similar setup to yours. Same size pool with a VSP and SWG (Circupool RJ45). I only need to run my SWG at around 20-30% during the heat of summer. Right now, it's only running at 10% and keeping up although it hasn't been very hot lately.

I run my VSP 24/7 at 1200rpm and, although I have my SWG connected to a timer, I just leave that on all the time as well. I decided to do this so the pool would be getting a little chlorine the entire day instead of only running the pump for the hours I needed at a much higher SWG output percentage. My thinking is that with some chlorine being made all hours of the day, the FC level will stay more stable and hopefully be less susceptible to getting algae. The pump electricity only runs me around $20/month so I don't mind just leaving it on continuously.

Also, I run my FC about 2 to 3 ppm higher than the target level according to the FC/CYA chart just to be safe in case something happens like a power failure. It's best to have a little extra chlorine than not enough, especially when the SWG is making the chlorine for me.

 

[birchdale]

How long do you run your VSP? I have a similar setup to yours. Same size pool with a VSP and SWG (Circupool RJ45). I only need to run my SWG at around 20-30% during the heat of summer. Right now, it's only running at 10% and keeping up although it hasn't been very hot lately.

I run my VSP 24/7 at 1200rpm and, although I have my SWG connected to a timer, I just leave that on all the time as well. I decided to do this so the pool would be getting a little chlorine the entire day instead of only running the pump for the hours I needed at a much higher SWG output percentage. My thinking is that with some chlorine being made all hours of the day, the FC level will stay more stable and hopefully be less susceptible to getting algae. The pump electricity only runs me around $20/month so I don't mind just leaving it on continuously.

Also, I run my FC about 2 to 3 ppm higher than the target level according to the FC/CYA chart just to be safe in case something happens like a power failure. It's best to have a little extra chlorine than not enough, especially when the SWG is making the chlorine for me.

That's very interesting, I like the idea of constant chlorine generation.
Currently the pump runs for 1 hour at 2000 rpm to skim, 2 hours at 2250 to sweep and 5 1/2 hours at 800 to just circulate. I also bump up the run times in the warmer season.
I'm switching our electric service plan to time of use, so can't run the pump during the afternoon peak period anymore, but will try your idea of longer hours at slow speed and low chlorine generation.
Off to Home Depot to rent a pump and stock up on chlorine.
Thanks again for the tips!

 

[DeanP66]

Just remember that you have to run the VSP at an rpm high enough to close the flow switch on the SWG or else it won't generate any chlorine. Try different setting by going down 100 rpm at a time and see when the no flow light finally lights up on your SWG. Then add at least 100-200 rpm to that to account for your filter getting dirty over time which will decrease the flow rate of the water. That will give you a good starting point on how low you can run your pump and generate chlorine.

I pretty much run mine at 1200 rpm all day, but I don't have a heater (which also requires a minimum flow rate). I have my skimmer pulling most of the water to create as much skimming of the water as possible. I still use a fine silt leaf net to pick up anything on top when I see it. I used to turn the pump on to 3200rpm for 30 minutes when I needed to vacuum the pool, but then I got a robot which put an end to that.

Basically, there's no reason to run your pump if you're not generating chlorine with the SWG, so always run it fast enough so it does. That way you can turn the SWG % down even further to save those precious hours (10-15k) that most generators are rated for.

 

[birchdale]

Thanks again for your help.
So the tile/waterfall cleaning and acid wash went well, the pool is filled with water again!
I have been running the pump continuously over the last couple of days and here are the latest numbers:
FC: 6.5
CC: pretty much 0
pH: 7.7
TA: 150
CH: 125
CYA 70 (I'm still adding powdered CYA)
CSI: -0.08
Temp: 77
I'm not too worried about the TA, since I will be adding acid and with the waterfall aerating, the TA should come down.
For the CH, the PoolMath app is suggesting adding 56lb of Calcium Chloride.
my questions are:
1. Should I worry about the CH at this time?
2. With CC at basically 0, do you still recommend performing a SLAM?
3. Is it OK at this point to add salt and install the SWG?
4. Anything else I should be doing?
Thanks!

 

[IceShadow]

I can answer #2 - is the water completely clear, no signs of algae? Have you tried doing an Overnight Chlorine Loss Test? With <1 CC and no overnight loss and no visible algae, no need to SLAM.

If you do need to SLAM stop adding CYA - your SLAM levels will be very high as it is at 70.

 

[DeanP66]

So, your numbers look good, but since you have a plaster pool, you definitely want a little more CH in there. You don't want the water to leach calcium out of your plaster, so I would raise it to 250ppm and stop right there. If you're like me in San Jose, your CH out of your fill water is surely quite high, so the CH will increase consistently over time, so it's best to start it on the lower end of the recommended level.

Once you do get your CH up to 250ppm, with the rest of your current numbers, your CSI will be a little high (+0.30), so you probably want to drop either your pH some of your TA to get that CSI slightly negative, so you don't promote early scaling, and that is especially important once you bring your SWG online. You don't want the plates scaling from high CSI and forcing you to clean them with muriatic acid. The more you clean them with acid, the shorter the lifespan of the cell, so keep a close eye on that CSI. Shoot for -0.3 to 0 at the highest. That should make your pool and equipment run optimally.

Update: Just looked back and remembered that you have a water softener for your fill water, so in that case, you could even go a little higher with the CH, but I wouldn't go much further than 300-350ppm at the most.

 

[birchdale]

I can answer #2 - is the water completely clear, no signs of algae? Have you tried doing an Overnight Chlorine Loss Test? With <1 CC and no overnight loss and no visible algae, no need to SLAM.

If you do need to SLAM stop adding CYA - your SLAM levels will be very high as it is at 70.

The water is new and never been so clear, I can't see any signs of algae. I will do the overnight chlorine loss test tonight.
Good point about the CYA! unfortunately, I just finished the last sock full, I think the CYA will be around 75-80 by tomorrow.
Let's hope I won't need to SLAM.
Thanks for your help, much appreciated.

 

[birchdale]

So, your numbers look good, but since you have a plaster pool, you definitely want a little more CH in there. You don't want the water to leach calcium out of your plaster, so I would raise it to 250ppm and stop right there. If you're like me in San Jose, your CH out of your fill water is surely quite high, so the CH will increase consistently over time, so it's best to start it on the lower end of the recommended level.

Once you do get your CH up to 250ppm, with the rest of your current numbers, your CSI will be a little high (+0.30), so you probably want to drop either your pH some of your TA to get that CSI slightly negative, so you don't promote early scaling, and that is especially important once you bring your SWG online. You don't want the plates scaling from high CSI and forcing you to clean them with muriatic acid. The more you clean them with acid, the shorter the lifespan of the cell, so keep a close eye on that CSI. Shoot for -0.3 to 0 at the highest. That should make your pool and equipment run optimally.

Update: Just looked back and remembered that you have a water softener for your fill water, so in that case, you could even go a little higher with the CH, but I wouldn't go much further than 300-350ppm at the most.

Sounds good, I'll get working on the CH.
I will keep an eye on the CSI, I certainly don't want to deal with scaling again, it got so bad that I disconnected the SWG and went to liquid chlorine. I now have a new cell and would like to keep it healthy as long as possible.
Should I take care of the CH before adding salt and installing the SWG?
Thanks a million for your continued help!

 

[DeanP66]

I would, so you can get your CSI where you want it before bringing the SWG online. Just be careful and don't overshoot. Add a little less than you need and test to make sure that it got to the level that you thought. Then make any other adjustment based on that result.

It would probably be in your favor to work on dropping the TA instead of the pH because pools with SWGs tend to push the pH up constantly, but once they get to around 7.7 or 7.8 it seems to slow down some, so that's probably where you will be maintaining pH for the most part. By dropping TA, it will help buffer the pH and keep it from climbing as fast, which means less acid needed over time.

One other option is also adding borates with boric acid, but I would wait and see how your pool and equipment react to having everything balanced first. I installed a SWG for my friend last spring and even though I kept the CSI slightly negative consistently, her high CH seemed to make her salt cell scale a lot. I was hosing that cell off weekly to clear the deposits before they hardened. This spring I decided to add borates to her pool and see if that helped. It has worked out very well. It's been about 2 months now with the borates and I haven't had to clean her cell even once and the kicker is that her CH went up to 750ppm (600ppm last year) so I'm pretty excited. Adding borates also buffers the pH climb as well. It seems to stabilize it even more, but the real benefit seems to be that it keeps the salt cell much cleaner.

Your mileage may vary, but again, I wouldn't even worry about borates until you get a good feel for your pool.

 

[birchdale]

Great info!
I have a similar experience with the pH always hovering around 7.8, the Borate sounds interesting.
Calcium Chloride will be delivered tomorrow so hope to get the CH up to the right level soon. I have ample supply of liquid chlorine, so no problem keeping the water chlorinated until all the numbers are right before installing the salt cell.
Cheers!

 

[birchdale]

The water is new and never been so clear, I can't see any signs of algae. I will do the overnight chlorine loss test tonight.
Good point about the CYA! unfortunately, I just finished the last sock full, I think the CYA will be around 75-80 by tomorrow.
Let's hope I won't need to SLAM.
Thanks for your help, much appreciated.

Got a late start on the overnight chlorine loss test but thankfully it has been cloudy today. In 13 hours there has been almost no drop in the chlorine level (certainly under 0.5). The combined chlorine remains under 0.5 and the water is still clear and no signs of algae. So it appear that there's no need to SLAM at this time.
Thanks!