Water Change Chemistry Question

[tbrown]

Ok, I'm mixing up some salt for a water change and both Hanna and Salifert say the new water is at 15.7 dKh.

Tank water is sitting at 8.3 dKh.

How do I figure out the new concentration if I don't lower the water change water alkalinity?

Tank volume: estimate about 125 including sump (125 tank plus 40 sump minus rock and sand)
5 gallons of new saltwater

My math may not be correct but it looks like the final concentration is going to be about 8.5-8.6?

 

[Slocke]

Ok, I'm mixing up some salt for a water change and both Hanna and Salifert say the new water is at 15.7 dKh.

Tank water is sitting at 8.3 dKh.

How do I figure out the new concentration if I don't lower the water change water alkalinity?

Tank volume: estimate about 125 including sump (125 tank plus 40 sump minus rock and sand)
5 gallons of new saltwater

My math may not be correct but it looks like the final concentration is going to be about 8.5-8.6?

Yep! 8.596

 

[tbrown]

Yep! 8.596

What equation?

I did ((8.3/100)*125+(15.7/100)*5)/130*100

 

[Slocke]

((8.3x120) + (15.7x5))/125 = 8.596

Make sense?

 

[gbroadbridge]

Ok, I'm mixing up some salt for a water change and both Hanna and Salifert say the new water is at 15.7 dKh.

Tank water is sitting at 8.3 dKh.

How do I figure out the new concentration if I don't lower the water change water alkalinity?

Tank volume: estimate about 125 including sump (125 tank plus 40 sump minus rock and sand)
5 gallons of new saltwater

My math may not be correct but it looks like the final concentration is going to be about 8.5-8.6?

Close enuf

Not sure if they may be some precipitation which lowers it a little which would depend on the pH of the new water.

 

[tbrown]

((8.3x120) + (15.7x5))/125 = 8.596

Make sense?

Yep! Same formula minus the /100 *100. Removes unnecessary steps.

Thanks!

 

[tbrown]

I also went in on the BRS Alkalinity calculator and reverse calculated it.

5 gallons at 8.3, want to raise to 15.7 equals approximately 1 tsp of Sodium Bicarbonate which changes 125 gallons at 8.3 to approximately 8.6.

Math... Love it and hate it.