Starting with City Water, PoolMath Seems to Mislead

[packetfire]

So, put 4,500 gals of city water into an above-ground pool, added my salt for the SWG, and took some initial readings:
pH: 8.2+ (Taylor chems, darker pink than the max reading on my gear, which is 8.2)
FC: 0 (Taylor DPD)
Alk: 40
CYA: less than 40 (lowest reading on tube)

So, added what "Pool Math" said:
22oz 7.5% bleach
7.1 oz muriactic acid
24 oz dry stabilizer

Waited overnight, running the pump on "recirculate" for 4 hours to mix everything nicely, and got this by the evening:

FC: 0.5
pH 6.8
CYA 40

Did nothing, ran the pump on recirculate another 4 hours

This morning, I've got:
Alk: 30
FC: 0
pH: 6.8
CYA: 50

So, now, pool math is suggesting:

Another 22 oz 7.5% bleach
32 oz of baking soda, to correct the overshoot on the Alk

I am a little concerned that we have a situation where multiple chemicals added within an hour of each other are frustrating things.

I assume that I adjust ALK first, when it is good, then pH, and when it is good, then FC.

I've not had this issue before - prior initial set-ups were uneventful, same pool, same test procedures and chems, same city water.

 

[ajw22]

What test kit are you using?

Don’t be a slave to the robot.

You should not make more then a 0.3 adjustment to pH at one time. Then retest and adjust again.

Add half the amount of baking soda and retest until your TA is 70.

 

[AK-]

I am a little concerned that we have a situation where multiple chemicals added within an hour of each other are frustrating things.

The issue is PoolMath recommended the CYA to fix the CYA and MA to fix the pH, however both are acids and both will have impact over pH and TA (Stabilizer will have a small impact, but compounds with MA). PoolMath does know what you addressing first or if you are in fact addressing any of them.

I assume that I adjust ALK first, when it is good, then pH, and when it is good, then FC.

Get FC up right away and keep it up.
As for TA/pH… it depends.
If you use aeration to raise your pH than do TA first.
If you use borax to raise your pH then do pH first and take the TA increase of borax into consideration for the TA.

 

[ajw22]

Chemicals suggested for raising TA. Their effects are:

• Baking Soda = big TA change, small pH change
• Borax = big pH change, small TA change
• Soda Ash/Washing Soda = big pH change, big TA change.

Get TA to 70 and pH will naturally adjust itself into the 7s.

TA - Further Reading

www.troublefreepool.com

 

[packetfire]

I guess the (mostly philosophical) question was overlooked - I was asking about the ORDER in which one should adjust various factors. I was always under the impression that TA was to be brought into line first, then pH, and only then FC. But what can one do in parallel, without working at cross purposes with oneself? The "two acids" mentioned by AK seems to be the most compelling evidence that one really can't expect to adjust more than one factor at a time.

Regardless, I'm getting there - 6pm Sunday:

Alk 60
pH 7.0
CYA 50
FC 0.5 (But the salt is now dissolved, so the SWG is tirelessly working on the issue)

And I don't buy "test kits", in answer to the question of "which kit?" - I buy reagents from Taylor (same as in the Taylor kits) as needed to test ALK, pH, FC, CC, CYA, and (for no apparent reason) hardness, and keep them in a very pretty wooden sextant case that hides an ugly tupperware container. I have an SWG, so once things get balanced, all I need to is add a little 20 Mule Team now and again, and change the sand in the tiny sand filter every 2 months, as it can become an algae farm, and sand is cheap while chemicals to kill algae in sand are expensive.

 

[duraleigh]

I was asking about the ORDER in which one should adjust various factors.

Any sequence would've worked. One after another in no particular order will make almost no difference.

Seem like you have your own path all figured out but the premise of this forum is accurate testing with those dreaded test kits! sorry

 

[PoolStored]

(But the salt is now dissolved, so the SWG is tirelessly working on the issue)

SWCG are really good at MAINTAINING FC. No so much RAISING FC.

I would suggest that you use Liquid Chlorine to get to your target range, then adjust the SWCG to maintain.

 

[MITBeta]

change the sand in the tiny sand filter every 2 months, as it can become an algae farm, and sand is cheap while chemicals to kill algae in sand are expensive

The only way that algae can get into your sand is if you let your chlorine level get too low for too long. All you need is chlorine to kill algae.