Questions about chemical balancing with new plaster installed ~35 days before closing

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chinatti

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May 7, 2014
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Massachusetts
Hi-

We've just (mostly) completed a renovation on our pool, and we're 21 days after plastering (20 days after initial fill). We will be closing the pool in about 2 weeks, so ~35 days after plastering. I've been following my PB's startup instructions, which were basically the same as the NPC Startup Card. Also, my pool is SWG, but I have not added salt (since the instructions say no salt for at least 28 days), and the plan suggested by PB is to wait and add in salt when we open in the spring and start the SWG up again at that point.

At this point I'm basically at:

FC=3-5, pH=7.2-7.5, TA=80, CH=225, CYA=70

At this point everything is mostly stable, except FC and pH needing adjustments every few days (with bleach and Muriatic Acid).

My questions are related to what chemical levels I should shoot for at closing, and how soon I should adjust.

A few questions:

1) PB instructions say to maintain those "FC=3, TA=80-120, pH=7.2-7.5, CYA=30-50, CH<=200" for 28 days. I'm inclined to start moving towards the TFP targets (FC=5-6, pH=7.2-7.5, CYA=70-80, CH=350-450, TA=60-80) sooner than that, maybe now? Any reason not to do that? CH is the one that will need the largest adjustment, and it seems better to me to try to slowly move up to the target as opposed to trying to bump the CH up ~200ppm to ~400ppm quickly before we close.

2) I'm curious what I should target for levels at closing. Any particular levels that I should pay particular attention to, or just keep them at the TFP recommended levels? It seems odd to me that the pH is bouncing around so much now and requires frequent adjustment, but when we close the pool we just forget about it until the spring...

3) PB says salt shouldn't be added for 28 days, and since this is very close to when we close, he suggested that we just wait and add salt after we open. Sounds reasonable to me - any reasons to add before we close?

4) We're using our PB to close the pool this year instead of the old company which we were never too impressed with. At closing the old company added Chlorine, algaecide, and scale/iron to the pool. Is there anything I should make sure that they do or do not add when they close this year with the new plaster?

Thanks in advance.....
 
Thanks. That link covers the general closing process, which I'm familiar with, and is done by the pool company. I'm looking for some more specific guidance on how to target my levels leading up to the closing since I have new plaster, and how I should weigh the short term level/targets vs the long term level/targets relative to my closing timeline.



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Wish I could be more helpful. You are in a rather unique position. Normally, I would say, do what the PB says while they are warranting their work. As soon as any warranty expires, I would switch to TFP methods.

I'm sure there will be someone along with more direct knowledge.
 
Maintaining the higher FC level is fine. It is common for PH to require frequent adjustment in a new pool. Getting your TA down to 60-80 will help to reduce the PH rise. Pool School - Lower Total Alkalinity. It is very important to keep PH at 7.8 or lower in a new plaster pool, and generally important all the time. I wouldn't be in too big a hurry to raise CH. What is the CH in your fill water? If it is 150ish then CH will rise as evaporation is replaced. I agree with adding salt in the spring. And no need to raise CYA above 30 or 40 when you aren't using the SWG. As for closing with fluctuating PH, I don't know because I don't close but I do share your concern. Getting your TA down to 60 or 80 is the best thing you can do to help PH. Yes, I would do that now.
 
My TA is around 70 at the moment, so maybe I'll try to push that down closer to 60 as a target before I close. That would make sense to help minimize pH rise. I'm not sure what the CH is in my fill water - but I don't expect to be doing any filling at this point until next spring, and I'm mainly concerned with what I should have as target levels before I close. I was assuming that it was important to try to get up to the 350-450 recommendation for CH before I close (and bought a bunch of calcium to do that), but maybe that's not a big deal?

My FC is not 3.5, but bounces around in the 3-5 range. I am targeting 5, and when it gets close to 3 I add some bleach.

My CYA is already around 70 - that was sort of a "mistake" in the sense that I was looking at the target levels for SWG pools (thinking I have a SWG), but obviously it's not on at the moment.

Really I'm trying to see if there's anything I should be targeting in the next 2 weeks before closing. Sounds like lowering TA a bit to help on the pH rise, and CH is still unclear to me.

Any other suggestions?
 
Thanks.

Yes, my FC is low - mainly because I'm so used to the SWG targets that I forget I'm really non-SWG at the moment. It's been holding FC well (and our temps are low - most pools by us are closed by now), so I don't think there was an issue. But I bumped it up a bit anyway to be safe.

So on the point of keeping CH at ~225 throughout the winter ... I only ask because if I plug in my potential levels at closing into Pool Math, I get:

With CH=225:
pH=7.5, TA=80, CH=225, CYA=70 @ 70 deg F -> CSI=-0.33
pH=7.5, TA=80, CH=225, CYA=70 @ 40 deg F -> CSI=-0.62 <- (BAD?)
pH=7.5, TA=80, CH=225, CYA=70 @ 30 deg F -> CSI=-0.72 <- (BAD?)

With CH=400:
pH=7.5, TA=80, CH=225, CYA=70 @ 70 deg F -> CSI=-0.13
pH=7.5, TA=80, CH=225, CYA=70 @ 40 deg F -> CSI=-0.42
pH=7.5, TA=80, CH=225, CYA=70 @ 30 deg F -> CSI=-0.52

If I drop the TA to 60, which was suggested to help combat pH rise, the CSI gets lower (i.e. worse):

With CH=225:
pH=7.5, TA=60, CH=225, CYA=70 @ 70 deg F -> CSI=-0.51
pH=7.5, TA=60, CH=225, CYA=70 @ 40 deg F -> CSI=-0.80 <- (BAD?)
pH=7.5, TA=60, CH=225, CYA=70 @ 30 deg F -> CSI=-0.90 <- (BAD?)

With CH=400:
pH=7.5, TA=60, CH=225, CYA=70 @ 70 deg F -> CSI=-0.31
pH=7.5, TA=60, CH=225, CYA=70 @ 40 deg F -> CSI=-0.60 <- (BORDERLINE)
pH=7.5, TA=60, CH=225, CYA=70 @ 30 deg F -> CSI=-0.70 <- (BAD?)

So ... my interpretation of this is that increasing the CH now before closing buys me a little extra buffer against my CSI dropping too low. And my big concern is affecting the new plaster / pebble finish ... Am I wrong about this?

(side note - if the pH rises up a bunch that also increases the CSI, and I'm not sure where the pH will end up after closing, so 7.5 may not be the right number there either.....)
 

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I think the advice given above is good.
The current readings should be okay because once you close the pool, the pH will likely rise (slowly) to about 7.8 - 7.9 which raises the CSI over the winter.
As the PB stated, starting out with a slight negative CSI is preferable for pebble pools.
If you are inclined to, raising the CH to 300 ppm wouldn't hurt.
 
With new plaster, pH rise and scaling are a risk. I would suggest that, as much as is reasonably possible, you should periodically pull back the cover and check the chemistry. If the ph gets too high, you can add acid and brush the pool to mix it in.

What cover do you have?

How soon do you expect to have a big snow load on the cover?
 
JamesW said:
With new plaster, pH rise and scaling are a risk. I would suggest that, as much as is reasonably possible, you should periodically pull back the cover and check the chemistry. If the ph gets too high, you can add acid and brush the pool to mix it in.

What cover do you have?

How soon do you expect to have a big snow load on the cover?
Click to expand...

Loop Loc cover- and snow could be any time, but I wouldn't expect it any time soon (plan to close in a week or so). Pulling back the cover to grab some water to test is feasible, but brushing the bottom would be a *massively* inconvenient undertaking. I would seriously hope I wouldn't need to do that. I would think that this chemistry balance over the winter with new plaster is a pretty standard "issue" with pools in this part of the country, and would hope that I wouldn't have to worry about doing that over the winter.....
 
If the cover is installed correctly, it shouldn't be too difficult to pull back the deep end part of the cover and brush the walls. If you have a deep end, brushing down the walls with a wide brush can create enough mixing to add chemicals.
 
JamesW said:
If the cover is installed correctly, it shouldn't be too difficult to pull back the deep end part of the cover and brush the walls. If you have a deep end, brushing down the walls with a wide brush can create enough mixing to add chemicals.
Click to expand...

I suppose - it just seems like kind of a hassle (maybe I exaggerated a bit there). In all reality, I might be convinced to check occasionally, but there's no way I'd be out there very often pulling the cover back, tweaking the levels, brushing, etc. What would you suggest I use as a threshold for adding chemicals? CSI falling below -0.6?
 
I'm more concerned about scaling due to high pH from plaster dust (calcium hydroxide). Just try to make sure that the ph does not get above 7.9.

Is the cover regular mesh, dense mesh, solid with a drain panel or solid with no drain panel?

As long as the springs are not too tight, they are fairly easy to install and remove
 

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