Bicarb Start-up

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bdavis466

bdavis466

TFP Expert
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Aug 4, 2014
5,615
San Clemente, CA
My pool is set to be plastered this weekend. We are going with Stonescapes Minipebble. I am planning to do the startup myself and would like to utilize the bicarbonate method from the recommendations I have seen here. I have never done a start-up myself...always just left it to the plaster guy to handle.

My plan is to outline the entire process and hopefully get some feedback from the experts if I miss any steps.

My fill water:

PH - 7.8
FC - 0
CH - 125
TA - 110

According to On Balance's post, 500-125+110=265. To raise my TA to 265, I need to add 130 lbs of bicarb.

Plaster goes in Saturday, acid wash Sunday morning and then begin filling. As the pool is filling I plan to check the TA and PH every few hours to make sure I'm on track. Should I try to keep the TA at 500 the entire fill?

It seems that a higher than usual PH is normal and not a concern(8.2)? Should I attempt to lower as I fill or wait until the pool is full?

In addition to the acid and bicarb, are any other chemical additions recommended? Sequestrant is recommended in this site's startup procedure. Is it needed? if so, which one?

Is there any need for calcium chloride?

Once the pool is full, I will run the pump for at least a week 24/7. Should I keep the pool and spa drains fully open as well as all of the returns so that both bodies of water are continuously circulated?

I plan to brush at least twice a day and test frequently. I will use tricolor tablets in the skimmers on the third day and keep the TA between 200-350. for the first month. I will then lower the PH to 7.6 and the TA to 80 (or lower?). Salt can then be added and I'll install the SWG.

Thanks for any help ahead of time!
 
The best reference is here. Bicarb startups don't come up very often, so I might have one of the minor details wrong, so check back to the document I just linked to.

You keep the fill water saturated with baking soda until you use up the amount calculated, rather than aiming for a specific TA.

During the fill you only lower PH if the fill water PH is above 8.3 to start with. Then you usually lower the PH when the fill is complete.

Sequestrant is good insurance, in case there are metal issues you are not aware of. Any of the recommended kinds of sequestrant is fine. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective. ProTeam's Metal Magic and Jack's Magic The Pink Stuff (regular), The Blue Stuff (fresh plaster), and The Purple Stuff (salt) are some of the top sequestrants. You can also find many other brands with similar active ingredients, some of which are noticeably less expensive.
 
Thank you Jason. The link you posted is what I referenced to get to this point. I just want to make sure I have everything lined up so there are no surprises.

As for circulating and filtering the pool and spa, should I just cycle back and forth between the two or keep both fully open?
 
I would put the spa into spillover mode, but manually over-ride the valve adjustment so the spa is only gently spilling over and you still have good circulation in the pool. The alternative is to run in spillover mode for one hour out of each six (or something similar).
 
As noted in the thread A Bicarb Start-up guide for TFP members, you calculate the TA that needs to be added as 500 - TA - CH from the tap/fill water. You do not normally add calcium chloride initially, but may need to add it during the maintenance period if it is below 150 ppm. The reason this rough rule of thumb works is that it has a roughly consistent saturation index which I show below at pH 7.6 and 8.0 and with a temperature of 77ºF (the pool water temp might be lower, especially from the tap/fill water) and ignoring CYA (i.e. the TA in the table is carbonate alkalinity).

. TA .. CH .... 7.6 .... 8.0 ... pHeq(for CO2 outgassing)
500 ..... 0 .... N/A .... N/A .... 9.09
450 .... 50 .. +0.01 . +0.40 ... 9.06
400 .. 100 .. +0.26 . +0.64 ... 9.01
350 .. 150 .. +0.37 . +0.76 ... 8.96 (minimum CH level to get to during maintenance period)
300 .. 200 .. +0.43 . +0.82 ... 8.91
250 .. 250 .. +0.44 . +0.83 ... 8.83
200 .. 300 .. +0.42 . +0.81 ... 8.74 (minimum TA recommended by bicarb start-up method)
150 .. 350 .. +0.36 . +0.75 ... 8.63
100 .. 400 .. +0.24 . +0.63 ... 8.46
. 50 .. 450 .. -0.01 .. +0.38 ... 8.17
... 0 .. 500 .... N/A .... N/A ... N/A

200 .. 350 .. +0.48 . +0.86 ... 8.74
200 .. 400 .. +0.52 . +0.91 ... 8.74
200 .. 450 .. +0.56 . +0.95 ... 8.74
200 .. 500 .. +0.60 . +0.98 ... 8.74


So you can see that the rough rule-of-thumb TA+CH sum to 500 gives an over-saturation of calcium carbonate through most of the range that is roughly in the +0.4 to +0.8 range for the pH from 7.6 to 8.0. If you were to have fill water that was unusually low in CH (< 50 ppm), then calcium may dissolve from and rise from the plaster. If you want to avoid that, then you could add some calcium chloride to your tap/fill water in the drum (i.e. mix it before you add it to the pool) and then adjust your TA addition downward to still follow the sum to 500 rule.

Remember that with the bicarb startup the idea is to convert calcium hydroxide that is produced during the curing of plaster into calcium carbonate at the surface in-place.

2Ca3•SiO5 + 7H2O --> 3CaO•2SiO2•4H2O + 3Ca(OH)2 + heat
Tricalcium Silicate + Water ---> Calcium Silicate Hydrate + Calcium Hydroxide + heat
Soft Uncured Plaster + Water ---> Hard Cured Plaster + Soft Slaked Lime + heat

Ca(OH)2 + HCO3- ---> CaCO3(s) + H2O + OH-
Calcium Hydroxide + Bicarbonate Ion ---> Calcium Carbonate + Water + Hydroxide Ion
Soft Slaked Lime + "TA" ---> Hard Limestone + Water + "High pH"

So with the above, the pH will rise with no change in TA (hydroxide substitutes for bicarbonate) and adding acid will lower both so that the TA will drop over time. If done correctly, there is no CH increase and no plaster dust. You want the TA to remain elevated above TFP guidelines during the first month so depending on its starting point (say in high CH water) and the amount of acid you add you may need to add baking soda to maintain the TA. After 3-4 weeks, you start lowering the TA by adding acid to maintain the pH and not adding baking soda.
 
As noted in the link,

In order to protect and help new plaster cure properly, the CSI of the tap water should be about +0.3 to +0.7 for about 2 to 3 weeks.
Click to expand...

Having the sum of TA and CH be around 500 and keeping the pH between 7.6 and 8.0 meets that criteria as I showed in the table in my post (unless the CH is low below 100 or high above 400). So after 3 weeks you can stop adding baking soda to maintain the TA as you've added acid so then the TA should drop with subsequent acid additions to get your TA to normal TFP recommended levels. You may also need to raise the CH to get to such recommended levels if you started out with low CH.

The basic idea of the approach is to have enough bicarbonate in the water to replace the hydroxide with carbonate in the plaster. You need enough calcium in the water to prevent the calcium from dissolving, but as shown in the table you have to get pretty low before that starts to become a problem that isn't easily compensated with more bicarbonate. If you want to add more CH to start out and adjust the TA accordingly to be more in the middle of the table and with a CH closer to where it will end up, you can, but you'd still want to target on the lower side of where you want to end up just in case the CH does in fact rise for whatever reason.

I went back and added to the table the pH of equilibrium for carbon dioxide outgassing since that varies with the TA level. You should minimize aeration of the pool water during this period of time because the pH will tend to rise not only from the plaster curing but also from carbon dioxide outgassing.
 
With the CH at 125 ppm, just leave that be and raise the TA to about 350 ppm.
Do not add any calcium chloride to the tap or fill water or especially the fill tank. Do not mix Bicarb with calcium chloride. After a few days to a week and with the pH staying below 8.0, then add some calcium chloride to 150 ppm or so. Then follow the other instructions.
 

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Alright...pool is plastered and acid wash in progress. The spa is full. I'm figuring 900 gallons. I added 48oz of bicarb and got:

PH:7.2

CH:175
TA:380 Total:555

Looks like I'm where I should be. I'm not sure why the ph went down from my fill water unless there was a little acid left over from the acid wash?

Pool should be ready to be filled in an hour...any advice?
 
Yes, there was some acid left over in the spa.

If you aren't using the barrel system while the pool is filling, you might want to try diluting some bicarb into a 5 gallon bucket of water and adding it to the pool after one thousand gallons has been added. Calculate the amount of bicarb for 1,000 gallons of water and add it after every 1,000 gallons of water has entered the pool.

May I ask what city you are in?
 
Riverside

The pool has about 1,000 in it. I just checked it and got:

PH:8.2 (or higher)
CH:100
TA:650

Apparently I've been a little too anxious with the bicarb so I'll slow down a little bit. I've probably added 15 pounds. I thought there would have been more acid left over.

I'm using a 5 gallon bucket with a hose attached and using that as a sort of mini barrel. Today is dedicated to watching water rise.

Why is the CH going down from my fill water?

Should I try to lower the PH right now?

Thanks again!
 
Yes, lower the pH with acid. But only add one fluid ounce at a time and check pH after about ten minutes. Dilute the acid into a bucket of water first. Don't add anymore bicarb until the TA is below 300 ppm. Looks like you need to reduce the dosage rate. You might be over-estimating the amount of water in the pool when you do the dosing with bicarb.
 
Since you are being careful about adding acid, increase the dosage to 2 ounces of acid with each treatment.
Don't worry if the pH doesn't lower right away. What you are doing will be and is beneficial.
 
this is a cool thread. I dont recall anyone posting the test results regularly DURING their plaster start up.

Man I said it a couple times during your construction thread, but that is one serously cool pool you built yourself !
 

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