60 Pounds of Dry Ice and a Swimming Pool!

I have used dry ice a few times for Halloween as shown in this image:

https://www.troublefreepool.com/~richardfalk/pool/Cauldron.jpg

I had some leftover and put it into my pool -- not 60 pounds, of course. It is neat to see, but it does lower the pH quite a bit (it doesn't actually change the TA -- for the same technical reason that outgassing carbon dioxide only raises the pH with no change in TA).

Adding one pound of dry ice to 10,000 gallons would drop the pH from 7.5 to 7.0 if the TA is 100 and if all of the gas dissolved in water. 50 pounds in 10,000 gallons would drop the pH down to 5.4. If 10 pounds of their dry ice dissolved into 350 gallons in the spa, then the pH could have dropped to 4.6 which is quite acidic. In practice, about half of the gas escapes (bubbles away) with smaller quantities such as the pound or so I added to my pool (my pool's pH dropped from around 7.5 to 7.2).

Richard
 

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So there is no change in TA just a PH drop? So how much does Dry Ice cost compare to Muriatic Acid? How long does the Dry Ice take to totally gas out? Handling the Dry Ice would be about as hazardous as pouring MA, but the fog show would much more entertaining.
 
Dry ice costs more than muriatic acid, and more significantly you can't store it at home for very long. If you really wanted to do this you would use bottled CO2 gas. CO2 is one of the ways to lower PH used by commercial pools.
 
I have actually been researching CO2 systems for PH control somewhat. I'm hoping to find a source for the phControl system made by the Clorinator folks as that would be a much cheaper solution then a CO2 system appears to be.
 
LostBoyinVA said:
I have actually been researching CO2 systems for PH control somewhat. I'm hoping to find a source for the phControl system made by the Clorinator folks as that would be a much cheaper solution then a CO2 system appears to be.

You can get a controller and solonoid for less than $100-150 - I use one for a fish-tank. Google "Milwalkee pH SMS 122" or look it up on e-bay.
 
Ok I was thinking about the cost factor. A gallon of Acid is costing me from Lowes rounded, but without taxes $7. A .5 drop in PH in my 32000 gallon pool is roughly half a gallon so $3. I have a Plaster Pool and a SWG so I get that much of a raise over a couple of weeks. The video claims a cost of $1 per pound of dry ice and the post above suggests a .3 drop in 10000 gallons per pound of Dry ice. So in my pool 1 pound is roughly a .1 drop in PH so I'd need $5 in Dry ice for a .5 drop in PH. So Muriatic acid is cheaper, but since Acid prices have doubled in the last couple of years, provided the dry ice price is acurate I'd say it may eventually be a cost effective alternative to acid. No I can't store it at home, but I have a grocery store that sells it 2 miles from my house.

So I guess I need to pick up a 1 pound block and see how long it takes to disolve and take a PH Reading Before and after to verify the .1 drop in my pool.
 
taekwondodo said:
You can get a controller and solonoid for less than $100-150 - I use one for a fish-tank. Google "Milwalkee pH SMS 122" or look it up on e-bay.

Thanks I'll look into it, but you then also need to buy a tank and pluming etc. So I'd suspect a DIY CO2 system for a pool is in the minimum $500 range. The Chlorinator is $140ish, I don't expect there PH Control system to be much more then that.
 
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