Calcium Hardness

[desmolift]

I'm new to the forum, but have been lurking all summer and learning a lot. I have a concern I thought I would ask the experts here, before I run myself into trouble. My calcium hardness has been dropping, started out at 250 and dropped to 230. I believe this is likely due to adding water, since my outside bib is pulling water through my water softener. I am using the Taylor K-2006 test kit. Here's my numbers as of today:

Temp - 80 degrees
FC - 4.2
pH - 7.5
TA - 100
CH - 240
CYA - 100+
Borates - 0
TDS - 500
CC - .2

I'm using PoolPal on my phone as a guide and using the Taylor tables as a cross reference. I've been trying to get my CH back up to 250. I have a 50lb bag of Calcium Chloride flakes 77% minimum according to the package. I added 8 lbs of Calcium Chloride expecting the hardness to move up 20ppm, but it only went up 10ppm (230->240), so I added another 5 5lbs, but the hardness didn't move at all. So, I'm considering adding another 5 lbs, but thought I would check in here first. Is this normal?

I know my CYA is high, I plan to deal with that post winter. Also, my Chlorinator is set OFF, getting off pucks.

 

[pooldv]

The test is +/- 10 ppm, so some variance there. If your CH tends to drift down it is fine to raise it to around 300 ppm in one shot to make it easier. Anywhere from 250 to 350 is good.

 

[desmolift]

So you're saying just keep adding Calcium Chloride until I hit the numbers I like? Even though the ppm calculations aren't working out? BTW, 300 would be another 26 lbs!

 

[duraleigh]

We suggest you use PoolMath on our site. It's what we know and it seems to on the money.

Do you have a spigot that bypasses the softener?

 

[banditig]

Since you're not going to use pucks any more, when you need more chlorine you can use calcium hypochlorite to raise CH.
but of course always test

 

[desmolift]

We suggest you use PoolMath on our site. It's what we know and it seems to on the money.

Do you have a spigot that bypasses the softener?

PoolMath gives me the same results, 4.4lbs to raise 10ppm. I've added 13 lbs and only moved 10ppm... weird.

Yes, I can bypass the softener for the whole house while filling the pool.

- - - Updated - - -

Since you're not going to use pucks any more, when you need more chlorine you can use calcium hypochlorite to raise CH.
but of course always test

Thanks, been using 6% bleach.

 

[domct203]

Your FC is way too low for your CYA.

You should do an extended CYA test to determine a better CYA level, then keep your FC greater than 7.5% of your CYA.

Start at step# 9:
Pool School - CYA

 

[desmolift]

Your FC is way too low for your CYA.

You should do an extended CYA test to determine a better CYA level, then keep your FC greater than 7.5% of your CYA.

Start at step# 9:
Pool School - CYA

Is there a relationship between CYA levels and Calcium hardness?

 

[domct203]

Is there a relationship between CYA levels and Calcium hardness?

Other than both effect your CSI, no.

 

[desmolift]

Ok... Got the CH to 260, added another 6 lbs of Calcium Chloride. So in all it took me 19lbs to move from 230 -> 260. I guess if the test variation is +/-10ppm then on the high side I would have been trying to move 40ppm which would have taken 18lbs. So on a stretch, I guess its within the margin of error.

 

[domct203]

Ok... Got the CH to 260, added another 6 lbs of Calcium Chloride. So in all it took me 19lbs to move from 230 -> 260. I guess if the test variation is +/-10ppm then on the high side I would have been trying to move 40ppm which would have taken 18lbs. So on a stretch, I guess its within the margin of error.

More importantly, where is your FC?

 

[desmolift]

More importantly, where is your FC?

Near 8.5 today. Measured CYA is coming in at 170, not sure how accurate this is given the 50/50 split of tap water. Recommendation for this is FC -> 13-20. Running with FC at 3-5, I'm getting algae growth on the walls after about 4 days, brush and vacuum. I'm increasing FC and watching for results, taking careful steps, while keeping the pool balanced.

 

[domct203]

If your CYA is 170ppm, your minimum FC is 13 (7.5%), target FC is 22ppm (13%), shock level is a whopping FC 68ppm.

If you have visible algae you need to lower that CYA more so you don't have to "break the bank" to pay for the chlorine needed to eliminate it. You will need to exchange most of the water in your pool. If you drain then refill half the volume of the water, the CYA will drop by 50%, getting you to around 90ppm (85 rounded up). Another 50% exchange will get you to 40-50ppm, which now only requires a shock FC of 16-20ppm.

Be careful with large drains (>40%), While it hasn't been too wet this season, a high water table can and will pop your pool shell out of the ground.