Pool Chemistry Startups

At a new plaster pool startup, are there service techs that have tested the tap water (that was used to fill the pool) and compared those readings with the water in the pool after it has been filled?   If so, what differences (or changes) have been noted in the pH, alkalinity, and calcium hardness?  What differences has been noted if the tap water was soft and aggressive versus balanced or hard tap water?


Also, has anyone experienced a significance difference in the calcium level changing during the first month or two?  We (onBalance) would like to get some feedback from service techs on pool chemistry startups. 

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  • David, glad you are happy with the results, and that also makes my day!

    One-half gallon of 31.5% acid will neutralize and is equal to 3.5 lbs. of Bicarb. The dosage can be flexible, but you should add more than that equivalent amount, because generally, you want to increase the alkalinity. 7 lbs. of bicarb in 10,000 gallons of water increases the alkalinity by 50 ppm. Even when the pH of the water is above 8.5, adding both acid and a lot of bicarb, will lower the pH.  If the pH is in the 7.5 range, adding a lot of bicarb only will not raise the pH very much. Bicarb is very soluble and safe to add.  The main trick for the plaster is to get the alkalinity up to at least 200 ppm.  That will stop the pH from rising extremely fast and high (IN new plaster pools only).

    One more thing. If the tap water has a high calcium hardness and alkalinity (a combined 500 ppm and above), there is no need to do a Bicarb start-up. Filling the pool with that type of tap water is essentially doing the same thing as doing a Bicarb start-up.  

  • Sorry for the delay

    Kim, can you give me a dosage rate for adding the bicarb with the acid?  ie 1 pound per 2 quarts or something like that.

    I had a service company do a modified bicarb startup on a dark gray quartz spa about 2 1/2 months ago.  We drained it this week to do some diamond polishing of the spa, and the plaster is incredibly hard!  We are using 50grit diamond pads, and having minimal "impact" on the plaster itself... it is so dense... Great!

  • David,

    The following are my observations of your start-up.  The tap water was slightly aggressive, about an LSI of -0.5, and therefore, the tap water dissolved (during the fill) about 60 ppm of calcium from the plaster surface, including some carbonate alkalinity. Although the water was LSI balanced after Day 1, after adding acid on several visits, the alkalinity was reduce, but the calcium rose higher.  

    I believe that if some sodium bicarbonate is added along with the acid (when reducing the pH), and by keeping the alkalinity higher for a few days, that less calcium would be removed from the plaster surface.

    I have also heard that Startup Tec helps reduce plaster dust.

    It is interesting that less than 1% calcium chloride was added to the mix. That is not very much for winter time jobs.  I assume you know that a one pound coffee can actually contains a little more than 1.5 pounds of calcium chloride. And that the amount of calcium chloride added is in relation to the amount of cement added, and does not include the sand or aggregate added to the mix.

    Good to know that waiting 6 hours to start the water actually helps on reducing plaster dust in your pools.

  • Most recent numbers (I keep forgetting to record them...)


    Project details: Pool only, approx. 14,000 gallons. Standard white plaster (0.5 -0.75% calcium added) Installation tempurature 60 - 70 F.  VERY low relative humidity >15%.


    Allowed the plaster to "cure" approx. 6 hours before beginning water addition.


    Added 1.5 bottles of Startup-Tec (been having very good results using this product the past 6-8 months) during the filling period, and 1 full bottle of Bio-Dex Stain-Off once the pool was full.


    All tests done with Lamotte ColorQ Pro test kit (solutions are 3 months old)


    Bypassed the heater, and fired up the pump within 24 hours, and ran it continuously for first 10 days. (water temp. approx. 55 - 60 F)


    Fill water:

    pH 7.4

    Alk 86

    CH 190


    @ 24hours

    pH 8.1

    Alk 150

    CH 250

    light to moderate amount of dust

    Added 3 quarts of Acid, thorough brushing


    Client brushes pool daily (often more than once)


    Day 2 (no readings recorded - sorry)

    added 1 qt. Acid brushed vigorously


    Day 3

    pH 8.5

    Alk 120

    CH 230

    added 1/2 gal. acid brushed


    Days 4-7 no readings recorded

    all days brushed

    day 5 added 1/2 gal acid


    Day 8

    pH 7.4

    Alk 85

    CH 390


    All subsequent visits have not been recorded , but very little change from day 8 readings have been seen... pool is stable at 2 1/2 weeks out


    We have just started the 6 hour wait to fill protocol on the past few projects, and have been very happy with the results... the pools seem to have significantly less dust. 

  • I use a LaMotte digital salt tester.  The 'Low Salt' alerts on chlorinators aren't reliable.  If the cell is dirty that light generally comes on along with the 'Inspect Cell".   As the cells get older it's a hassle keeping them calibrated, so their readouts become "ballpark" estimates of the salt level.  The LaMotte can be calibrated in 5 minutes, so I only rely on that tool for a accurate reading of salt.




  • Kevin


    The builder is partially right that with auto fills leaks can go undetected. We put an auto fill on every job. We will however will not activate it for at least 2 weeks after the pool is filled and operating. When I'm satisfied there is no water loss (obvious amounts) I begin use of the system.

    Water features, waterfalls will contribute to some water loss from splash out and evaporation.

    In regards to the salt, if you have a significant water loss, your salt system should have an alert indicating a low salt level. That will be a dead give away of some type of water loss. Make up water dilutes your pool water and requires additions of salt.

  • Day Five:  pH: 7.0, CH: 150, TA: 90.


    Pool is sparkling, little dust left.  Will soft-brush vacuum on Friday (Day 7).


    Have been having conversations with owner about installing a 'Dig' digital autofill on the water-fill valve.  Builder is of opinion that leaks go undetected with auto-fills.  With this being a salt pool I think weekly monitoring of the salt level with a digital salt tester will show leaks.  I see more yards flooded with the old manual fill systems and have yet to see a leak go undetected too long in a salt pool. 


  • Hydrazzo finishes are diamond polished one day after application.

    We have done quite a few in the last year. Yes, the plaster dust is cut considerably because of the polishing process. It also provides a silky finish, not slippery, exposing the aggregate beautifully.

    We still find we have to brush a little dust but not nearly as much as say a traditional plaster finish or even a Diamond Brite finish.


    My plaster contractor suggested a start up chem which we have found be very good. Here's the link: www.mcgrayel.com

    Startup -Tec decreases the dust and helps control metals, etc.. You still have to test your fill water and your pool water as usual. We have found it to be very effective.

  • Question...


    Aren't Hydrazzo pools diamond polished (often for multiple days) prior to filling?  That would have a pretty dramatic effect on things like amount of dust etc.

  • Morning session at the new hydrazzo shows:  FC=1.0, TC=2.0.   pH=8.0,  alkalinity=150. CH=150, phosphate level =0


    I'm treating the phosphates daily.  Used a non-phosphate 'stain-out' product on first day.


    Not much dust, the filter pressure is same as yesterday.  Since this is a Pentair Quad/DE filter I can backwash/clean the cartridges everyday.


    I called the pool plumber who installed the equipment ( and did a nice job too).  The pipes were threaded into the skimmer.  Cut the U-joint fittings off at the top of pipes and then got each pipe out with a big pipe wrench.  They were 'sand-welded' in too - lots of gunite debris in/around bottom of skimmer - took some effort to get them out.


    The plumber ID'd the secondary valves (pool cleaner and spa bypass) so now things make sense to the owner...and me. :)


    The high calcium in the fill water is notable from my experience around here.


    Early next week we'll have the heater taken apart and cleaned.  It's a 8-10 y.o Laars and runs well but, this seems like the time to get it tuned up.


    Owner hopes to be swimming on Monday.  My guess is that the dust should be gone by then and they'll be able to swim.


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