Controlling high pH in spa

[pgershon]

I have a 2500 gal spa (diamondbrite finish) next to my pool with its own water (separate circulation from pool, it’s own SWG). I’ve just started maintaining system myself. I have brought TA down from 120 to 70 over the past week with Muriatic acid, but I can’t get the pH to stay below 8.0.

Spa runs almost daily at 104 degrees (cools to 85 at night) and jets and air blower run 10 min/day or so. I’m sure the aeration is driving up pH, but that is the spa’s function.

Any ideas to bring pH down to 7.4-7.6 where I don’t need to add acid daily?

total chemistry:

fc 9.5
pH 8+
TA 70
CH 300
CYN 50
Salt 3200

 

[Mdragger88]

I keep my spa ta around 50 it helps keep the ph rise down. I also use 50ppm borates via boric acid after ta is where i want it.

Borates - Why and How

Borates - Why and How Why Adding borates can improve your experience with your pool, but is completely optional. If you do plan to use borates, wait until everything else is settled down before adding borates, especially TA and PH. The only situations where we specifically recommend using...

www.troublefreepool.com

 

[cowboycasey]

You will likely always have to add MA daily.. You can try to get your TA down between 40 and 50, Might get you a couple days between adding MA...

You may look into an auto dosing MA system... Here is a thread and there are many more

Acid pump options - DIY - Stenner - or? (settled on Pentair Acid Tank w/Pump)

Thanks to a few current threads on acid automation I am doing some research on adding a acid dosing setup for my pool. I am not yet sure how all of this will work - I do have a basic idea of what I want and I think I know what I need to do IF I decide to do this say next spring... 1. Chose one...

www.troublefreepool.com

 

[pgershon]

So I have my TA down to 50 and the pH is now relatively stable for two days in the 7.6 range.

But now I am concerned with CSI at low TA. I just recently brought my CH up from 70 to 325. But it looks to me like I need to go to the 500+ range to get CSI into a reasonable range. My temp varies from 85-104.

FC 8.0
pH 7.6
TA 50
CH 325
Salt 3200
CYN 50

Am I missing something?

 

[cowboycasey]

with TA at 50 will your PH raise and stabilize at 7.7 or 7.8, that is where mine likes it and can stay there for a long time before I need to add acid.. If your fill water is not high in CH then adding a little more CH to be able to keep a lower TA should not be a bad thing..

What is your CSI at now?

 

[pgershon]

CSI=-0.42 using pool math. To get above -0.30, I would need to substantially boost calcium. That is what I wanted guidance on as it’s hard to lower CH once you get high numbers

 

[cowboycasey]

it is a little low.. can you aerate your water a little and see if your PH will stay at 7.8 or so.. that will get you closer to -0.30

I am not sure if a higher TA or Higher CH is better for your situation... the lower TA is what you want so you can add less MA so really I guess a higher CH is the only way you could have both...

Other than that I am out.. I have a liner pool and do not want to give you bad info for your pool...

 

[pgershon]

Any suggestion from others with lots experience on low using TA with plaster spas? @mknauss or anyone else? Should I raise CH to 500+ to better accommodate TA=50?

 

[mknauss]

I do not have a plaster spa.
However, one issue in your climate with higher CH is winter temperatures. We seem to see alot of issues in the winter with plaster spas. Scale creation (crystals) though whether that is tied to high CH or other chemistry issues is less evident.

I would not go above 400 ppm CH if possible. A slightly negative CSI is not an issue. Your TA of 50 with your CYA level of 50 is leaving you with around 30 ppm carbonate alkalinity. Have you considered using borates?

Borates in pool - Further Reading

www.troublefreepool.com

 

[JoyfulNoise]

2500 gallon spa ... it's basically a small pool and not a hot tub. Unfortunately plaster spa's are very difficult to manage because plaster surfaces require more strict adherence to proper CSI levels. In an acrylic hot tub, you can get away with fairly low CSI because it's relatively unimportant; in a plaster spa you ned to maintain better control.

My suggestion is to keep the TA around 60ppm, the CH at around 400ppm and your CYA a little lower, perhaps 30ppm. Keep your pH above 7.6 and try to target 7.8 as much as you can. Adding borates will help with pH rise. You should keep the spa covered with a bubble cover and try to maintain the temperature lower (say in the mid 80's) and then only ramp it up to hot tub temps (104F) when you absolutely have to. Yes, you are going to use more energy from your heater doing it that way but that's the price you pay for an atypical setup.

As for recirculation, are your air jets always on? Do you have a recirculate feature with returns that don't use air? If not, then you should automate the air intake to close it off when not need and that way the aeration is reduced.

 

[pgershon]

Have you considered using borates?

I have boric acid on order. Started with 5 lbs. What is the best way to measure PPM borates?

 

[pgershon]

My suggestion is to keep the TA around 60ppm, the CH at around 400ppm and your CYA a little lower, perhaps 30ppm. Keep your pH above 7.6 and try to target 7.8 as much as you can.

Thanks. I will try that. My spa shape is very irregular - basically an eye with a 2.5'x2.5' bench all around. Size is estimated but based on chemical additions and taylor reading after, 2500-3000 gal. I got TA from 120-100-90-80-70-50 but somehow missed 60 going down. At 0, pH creeped up fast. At 50 its been pretty stable. I guess a little baking soda is needed now. Should I wait and add before or after the boric acid (which should arrive this week).

As for recirculation, are your air jets always on? Do you have a recirculate feature with returns that don't use air? If not, then you should automate the air intake to close it off when not need and that way the aeration is reduced.

The filter pump runs 12 hours and is probably too fast for the size of the pool (single speed 1.5 hp pump). The air jets and air blower are on their own circulation and just turned on when someone is in the pool. The aeration is totally overkill to (its a GAST professional $2500 unit - when it dies I will go with something in the more reasonable residential line).

 

[JoyfulNoise]

OK, just looked up that blower ... wow, that is crazy overkill!! I don't know who built your pool, but I think they went a bit too far. Then again, that pool is out in the Hamptons (I grew up in Setauket ...) so they must figure that money is no object out there ... what is Alec Baldwin like as a neighbor??

Anything you can do to reprogram and stop those jets from running unless they are absolutely needed, will help to keep the aeration down. A cover will lower the rate of outgassing of CO2 and keep the pH more stable.

What is your fill water pH/TA/CH like? Can you go measure it? You may not have to add any baking soda if you can replace water, it will come up on it's own if the TA is high enough. If not (LI water can be very soft and acidic), then you can use baking soda AFTER you add borates.

Just get test strips for now for borates. My signature has a drop test procedure for borates in it but you'll get this done quicker with strips.

 

[pgershon]

OK, just looked up that blower ... wow, that is crazy overkill!! I don't know who built your pool, but I think they went a bit too far. Then again, that pool is out in the Hamptons (I grew up in Setauket ...) so they must figure that money is no object out there ... what is Alec Baldwin like as a neighbor??

Lots of what I have is overkill, but that did not stop the builder from skimping on the rebar. I have spent over $100,000 in crack repairs over 20 years - 3 major repairs done although I believe it was finally fixed 3 year ago. And we live in the woods - no fancy neighbors.

What is your fill water pH/TA/CH like? Can you go measure it? You may not have to add any baking soda if you can replace water, it will come up on it's own if the TA is high enough. If not (LI water can be very soft and acidic), then you can use baking soda AFTER you add borates.

Fill water is filtered (whole house water filtration system). Well water is very acidic and contains iron in high concentrations. I tested the "filtered" water:

pH <7.0
TA 120
CH 80

Boric acid and test strips on order.

 

[JoyfulNoise]

So no visits from Billy Joel then?

Your fill water data is very revealing - low pH and high TA (unusual for Long Island) means that you essentially have club soda coming out of your faucet. The low pH forces the TA to covert from bicarbonate to dissolved carbon dioxide which then out-gasses and raises pH (much like opening a can of soda). What that all means is you need to top of your pool as little as possible or else all that high TA fill water is going to drive your pH up. As I said above, a simple bubble cover on the spa when not in use will go a long way to controlling pH rise. It will also cut down on evaporation and heat loss thus allowing you to recirculate water with less energy expenditure from the heater. Using the blower as little as possible will help too. Borates and 60ppm TA should keep your water at 7.6-7.8. Let it rise to 8.0 before using acid to knock it down. Don’t go below 7.6.

 

[pgershon]

I have my own softening system on the water.

 

[pgershon]

low pH and high TA (unusual for Long Island) means that you essentially have club soda coming out of your faucet.

Actually, I just looked at the unfiltered water that comes out of the garden line and is something I could tap into for the pool (instead of the softened water). It is substantially more acidic and lower alkaline. Do you think its worth switching? Kind of makes sense to me given my issues.

Well water:

pH = 6.2 (approximate based on test strip - I have a pH meter on order - cannot measure this low with taylor test)
TA = 30
CH = 25

Filtered water (currently the fill water):

pH = 6.8 (approximate)
TA = 120
CH = 50

 

[JoyfulNoise]

What kind of well water filtration system are you running?

 

[pgershon]

Not 100% sure what was installed two years ago. For 10 year I had separate water softening and acid neutralizing systems. But it was replaced and I was busy at the time and did not pay attention. Looking at equipment and cannot say for sure.

That being said, appears to be a calcite system for tasing pH. I am guessing that I am dissolving calcium carbonate in water and then removing the calcium, since its not present in fill water either (but actually higher level than the well water).

 

[JoyfulNoise]

Yeah. You definitely have a remineralization post filter, probably crushed limestone. It’s adding both mineral hardness and carbonate alkalinity. You’d be better off filling the pool/spa with the untreated water as long as there aren’t metals in it like iron.

You can fill up a 5 gallon white plastic bucket with a gallon or two of untreated water and add 2 cups of bleach. Let it sit for a while and see if the water turns tea colored. If so, you have iron. Long Island well water is full of iron.