Soda ash PH rise vs Kalk?

[Heabel7]

I was wondering if my ph swing is normal for soda ash vs Kalk. Soda ash seems to do a better job.

Currently dose a bit of soda ash to compensate for not having enough evaporation for Kalk to fully replenish my Alk consumption.
-100 Gallons total volume.
-Brs Soda Ash 15ml raises PH about .02
-Brs Kalk fully saturated (no probe to test, just add more than directions and stir for 3min) 55ml raises Ph .01.
My bag of Kalk has been sitting on the shelf for a couple years and thought it may not be saturating as if it were new.

I have alot of CO2 in my air therefore the PH drops rapidly after the addition of either, but the PH boost from Kalk disappears quicker based on my graphs. Is this normal? From reading the forum, Soda ash ph is lower than saturated kalk, so I though Kalk would give a larger boost.

Based on my observation i should be dosing my soda ash overnight to maintain PH vs Kalk. Counter to all the rage at the moment.
!

 

[Randy Holmes-Farley]

The pH boost from carbonate (e.g., sodium carbonate / soda ash) is a tad less than half as much as from hydroxide (e.g., kalkwasser or sodium hydroxide) per unit of alk added.

 

[Heabel7]

So my kalk is not giving the boost it should?

 

[Miami Reef]

So my kalk is not giving the boost it should?

I read a post recently where someone wasn’t having the ph boost from kalk they expected despite “overdosing” their ATO. At the end they realized they were using a much smaller spoon size and didn’t even saturate the ATO 50%.

Are you using the correct spoon measurements?

 

[Randy Holmes-Farley]

So my kalk is not giving the boost it should?

Seems right to me. You just are adding hardly any. 55 mL in 100 gallons only boosts alk by less than 0.02 dKH. Adding 1.4 dKH boosts pH by about 0.65 pH units.

 

[Heabel7]

I read a post recently where someone wasn’t having the ph boost from kalk they expected despite “overdosing” their ATO. At the end they realized they were using a much smaller spoon size and didn’t even saturate the ATO 50%.

Are you using the correct spoon measurements?

Rather than try and get exact because I don’t have a way to measure saturation at the moment. I add more. I’m using a five gallon bucket. I put approximately 15 tsp in just to be sure. And I have a very thin layer of kalk slurry sitting on the bottom. Most say 2tsp for saturation but BRS says 1.5. So I think I’m good…… I have a ph probe pen on order to confirm.

 

[Heabel7]

Seems right to me. You just are adding hardly any. 55 mL in 100 gallons only boosts alk by less than 0.02 dKH. Adding 1.4 dKH boosts pH by about 0.65 pH units.

I’m adding 55ml every 15min over a 12 hour period 7pm- 7am overnight for a total of 2640ml. That’s my current evaporation rate (with my turbulent flow I thought I would have more).

it has been hot outside here in Chicago. House closed up for days. Based on my graph I’m assuming that co2 is building in my home day after day especially with the kids home from school.(1,400 sq ft, 5 people and a dog). Is that correct?

looking at the overnight. You don’t see Mimi bumps until late in the process. Why is that?

before I ran my skimmer line outside, I seen a dip to 7.7 overnight without kalk. I imagine before line outside and kalk I had to be getting dangerously low, possibly into the 7.6’s..Probably…..right?

 

[Randy Holmes-Farley]

I don’t know how low in pH you were getting, but your evaporation is fairly low, and you are only adding a total of 0.7 dKH per day with the limewater (assuming it is saturated). If that meets your alk needs, then it is all you can do with additives, but if you can take more alk, you can use sodium hydroxide. That said, your pH looks ok to me and you won’t detect the individual additions spread out like that.

The max pH attained is much lower when you spread out the dosing, but that’s better than a spike followed by a decline back to normal levels and I think spread out dosing strains a higher average pH.