High traffic public spa pH

[bigpete]

I have done my best to search for the answer but I haven't found it yet.

I work at a pool as a head guard and I manage a pool (120k gallon) and a spa (1500 gallon).
The pool has been extremely easy to manage, very few fluctuations.
*This is indoor facility in Texas, and cyanuric indoors is explicitly against health code.

But the problem is the spa. It has fairly high traffic but the aeration is on anywhere from 60% to 90+% of the time I'm here (5pm-9pm). The pH skyrockets if I add enough bicarb to reach even 60 TA.

Outside of checking on it more often what should be done as a buffer? I work about every other night and no one else manages the TA and most days the TA is ~20 when I start my shift. I'm worried about the plaster.

I want to try to keep the TA at 40-60 but its so unstable at that range I can't keep it there. We have an ORP sensor so as soon as the pH rises (and the pH probe needs calibration) the FC just explodes upwards.

1 Would borax help much?
2 What should I attempt to keep the TA at?
3 What should I try to keep the pH at? (for the saturation index and FC needs, 2-8)
4 What should be done about the CC, at the end of the night it seems to usually be 1.0-1.5


Using a Taylor k-2006 test kit.

 

[kimkats]

You are in a hard place for this pool and spa care in that you HAVE to follow the rules for PUBLIC pools AND it is indoor. Your "rules" are far different than a private pool.

Play with the TA and see where the pH likes it to be. That is what is most important thing to work with.

As far as borax.........is that allowed by your rules?

Kim

 

[Arizonarob]

@JoyfulNoise Our resident chem guru will be along to see if he can give you some advice. Hang tight.

 

[Jimrahbe]

Let's also see if @JamesW has any inputs..

Jim R.

 

[JamesW]

Do you have an acid feeder that responds to the pH?

What do you mean that the TA is unstable at 40 to 50?

I would keep the pH as high as possible within the rules you need to follow.

The TA should not be unstable at any level unless acid is being added.

 

[bigpete]

Sorry for the delay! The TA seems fairly stable at ~20-30 but that puts the saturation index pretty fair in the negative. When the TA is 50+ the aeration+people+chlorine feed seems to skyrocket the pH. When the sensor is doing its job properly it is still downstream from the water so it takes a few minutes to respond to changes and tanks the TA from the acid feed.

The pH sensor may be dying out so I have been checking pH every hour or so. Would having the set point on the controller higher (and adjusting the ORP set point as well) work well enough?

Do you think a CO2 system would be of much help? This city doesn't have much money so I'd have to make a pretty convincing case for any modifications. I've asked about a UV system and been told they aren't convinced its worth the money

And legally for borax I haven't been able to find anything explicitly or implicitly banning its use. The closest thing I could find was: "Use of registered products at post-10/01/99 and pre-10/01/99 pools and spas. In post-10/01/99 and pre-10/01/99 pools and spas, only chemicals registered and labeled for use in pools and spas by U.S. Environmental Protection Agency shall be used."

An average reading for the spa seems to be
FC: 2-5
CC 0.5-1.5 ( ? )
pH 7.2-7.7
CH 150-250 (I manage this directly, fill water is about 150)
TA 20-30
Temp: 98-100

 

[mknauss]

Keep your pH near 8 and the low TA is not of much consequence as long as the pH is stable. The elevated temperatures keep the CSI from getting too negative.

I suspect your fill water TA is in the 80ppm range?

A bump in calcium would also help. Use of Cal Hypo at closing would add that.

 

[bigpete]

Testing the tap water (after letting it run for a few minutes) has given me an average of 104 ±9 TA and a pH of 7.78 ±0.15 with 5 tests.

What do you think I should set the calcium level to? The charts that I found online to calculate it weren't giving me a big difference from bumping it from 250 to 300 or more.

I'm nervous to put the pH that far out of the ordinary due to the imprecise pH sensor. Right now I've set it to turn on when the pH hits 7.7 but it's swinging so wildly that I don't have enough experience to know if it's making much of a difference.

I cleaned it a few weeks ago so in the next few weeks we will see if it needs replacing or not.

EDIT: I don't have a TDS meter or a way to measure the salt concentration for a more detailed calculation

 

[mknauss]

A higher pH (within reason) has little consequence other than the potential to scale.

Use Poolmath to calculate your CSI. I used a TA of 30, a CH of 200ppm, and a temperature of 100F to get a CSI of -.46. Raising the CH to 300 ppm gets the CSI to -.29

 

[bigpete]

Oh and looking at the heath code again, Texas has the max pH of 7.8

Is leaving the salt area on poolmath as is going to still give reliable enough numbers to change chem levels on?

 

[mknauss]

All pool water has salt (salinity). Poolmath assumes a low level of salinity ppm as long as you select the primary source of chlorine is Bleach.

Not much to say about the pH requirements. No science behind it, just a number from them.

 

[bigpete]

So with more attention to maintain the pH I should just need to bump the calcium level and just aim to keep the TA as is at 20-30?

To change the ORP set point to keep with a similar FC level is that going to just be a guess and check type situation or is there a rough guess formula?

 

[mknauss]

As long as the pH is stable, the TA can be whatever it is. A higher CH will protect your pool plaster.

ORP is not in the realm of this forum. They are not reliable and thus we do not recommend their use. As you are a commercial pool, you have other requirements.

 

[wogster]

As long as the pH is stable, the TA can be whatever it is. A higher CH will protect your pool plaster.

ORP is not in the realm of this forum. They are not reliable and thus we do not recommend their use. As you are a commercial pool, you have other requirements.

In some jurisdictions, TA is regulated, and must be between certain values (around here it is 80 and 120, if it is out of spec, the health inspector can close the pool, and it can take forever and a week getting them to come back to open it again.

 

[mknauss]

(around here it is 80 and 120, if it is out of spec, the health inspector can close the pool, and it can take forever and a week getting them to come back to open it again.

Not science - just rules.

 

[bigpete]

In some jurisdictions, TA is regulated, and must be between certain values (around here it is 80 and 120, if it is out of spec, the health inspector can close the pool, and it can take forever and a week getting them to come back to open it again.

Texas doesn't specify for that at least. The closest I could find was:
"Test(s) for total chlorine, cyanuric acid, alkalinity and hardness at post-10/01/99 and pre-10/01/99 pools and spas shall be conducted as necessary to assure proper chemical control."

Other than that the closest they come is defining it and saying it can lead to scale if too high.

But outside of closer monitoring is there much else I could do to stabilize the pH? Being a spa it has fill water coming in mildly often so I don't think it can easily bottom out. Does the higher calcium level have any buffering capacity?

 

[wogster]

Not science - just rules.

True, however when the rule maker, can shut you down, and issue a big fine if you don't abide by the closure it doesn't matter how stupid that rule is.....

 

[bigpete]

True, however when the rule maker, can shut you down, and issue a big fine if you don't abide by the closure it doesn't matter how stupid that rule is.....

FWIW, I have yet to see an inspection. Idk how often but I can't imagine they're very strict tbh. At the pool I'm at we don't have a timer on the spa aerator

Thanks for the help guys! Made me feel much more confident in the answers I was giving my boss!

 

[wogster]

FWIW, I have yet to see an inspection. Idk how often but I can't imagine they're very strict tbh. At the pool I'm at we don't have a timer on the spa aerator

Thanks for the help guys! Made me feel much more confident in the answers I was giving my boss!

Depends on where you are, we see the city health inspector every 3-4 months. We actually got a conditional pass once, because the timer ran 15 minutes and 10 seconds, instead of 15 minutes max....

 

[Pdxonthego]

I have done my best to search for the answer but I haven't found it yet.

I work at a pool as a head guard and I manage a pool (120k gallon) and a spa (1500 gallon).
The pool has been extremely easy to manage, very few fluctuations.
*This is indoor facility in Texas, and cyanuric indoors is explicitly against health code.

But the problem is the spa. It has fairly high traffic but the aeration is on anywhere from 60% to 90+% of the time I'm here (5pm-9pm). The pH skyrockets if I add enough bicarb to reach even 60 TA.

Outside of checking on it more often what should be done as a buffer? I work about every other night and no one else manages the TA and most days the TA is ~20 when I start my shift. I'm worried about the plaster.

I want to try to keep the TA at 40-60 but its so unstable at that range I can't keep it there. We have an ORP sensor so as soon as the pH rises (and the pH probe needs calibration) the FC just explodes upwards.

1 Would borax help much?
2 What should I attempt to keep the TA at?
3 What should I try to keep the pH at? (for the saturation index and FC needs, 2-8)
4 What should be done about the CC, at the end of the night it seems to usually be 1.0-1.5


Using a Taylor k-2006 test kit.

We have 9 spas And no matter what the issue is Temp, Bather load, and body of water.

I would check the feeeds and see if you are using the same Chlorine pump size or tubing and or if your Chemtrol or system is set like a Pool. Often the health clubs set them the same and do not think of the body of water so over feeding throws things off..


are you using a True PPM like 255? Or a ORP sensor 250 ? (For chemtrol)

i would consider the feed rate and proportional feed as well...


do you use CO2 ? For PH?

I will ask my staff for a response to your issue.,.. as I handle the building not the aftermath