Did my CH really rise this much?

[rhythm]

Hello, not sure if my CH is really this high or if my testing is not accurate....

Our tap/fill water is normally quite hard (tap can often be 300-350 ppm or more). For the last couple of years, anytime I've measured the CH of my pool it's been in the 350-375 ppm range. Because it's been very consistent, I hadn't checked it for several months. Today I checked it and measured around 850 ppm! I repeated the test and got the exact same result. Just to see whether or not I would get an unexpectly high number for our tap water, I tested it and measured 200-225 ppm. This is actually a little bit lower than I expected for our tap water, but it still seems reasonable, knowing that our water hardness does fluctuate throughout the year. So....

1)Could the 850ppm really be correct for my pool? I basically just use liquid chlorine to sanitize (no cal hypo ever). What factors would make it rise to this level? BTW, pH is currently 7.4 (just lowered it a bit yesterday - it likes to rise if I don't stay on top of it with acid), and my TA is at 80 ppm (it's been 70-90 ppm pretty consistently for the last couple of years).

2)Is there an issue with my test? I'm using the Taylor reagents and a magnetic stirrer. I did get what I initially thought was a fading purple endpoint, because at one point the sample stayed the same purple shade for several drops. But eventually it did change to the pure blue color that I expected, and stayed the same blue shade after a couple more drops. (I did not get any 'hanging purple' when doing the tap water test, but the CH level was a lot lower in that case.)

Regarding the purple, I know that once the color changes and remains the same, the test should be considered over. But then again, after more drops I did get to the blue color. And if my CH was really 850 I can see that it might be reasonable for the sample to be red/pink for quite a while (and it was), purple for a while, then finally the expected blue color.

Thoughts or help? The CH test did eventaully reach the normal blue color that I expected, so it seems like it worked OK, but the CH result I got for my pool sure seems unreasonably high.

Thanks,
Greg

 

[Guest]

Greg,

Based on your information, it is probably that high. Evaporation and our water source out West has our tap water high in CH over the last couple years. When was the last time you drained (bad word) or purified your water?

 

[PaulR]

Expanding on what salp said: Over time, water evaporates from the pool. It doesn't take any calcium with it. Then you add more tap water to pool, which adds more calcium. Over time your CH will keep going up.

That said, going from 350 to 850 is one heck of a jump; more than double. I can see you live in the Southland but even so, normal evaporation wouldn't account for that in just one year. (In a few years, it's more plausible; one year, harder to believe.)

There might be a testing issue here. You know there are two ways to do it, right?
The usual way is a 25ml sample, 20 drops R-0010, 5 drops R-0011, then each drop of R-0012 counts as 10ppm CH.
The other way is a 10ml sample, 10 drops R-0010, 3 drops R-0011, then each drop of R-0012 counts as 25ppm CH.

If you get similar results both ways (around 85 drops the first way, around 34 the second way) it's probably right.
--paulr

 

[Guest]

We did a pool not far from you (Dove Canyon) earlier this year, and took the CH under 200 (I can't remember exactly where) and she is already up to 450 (IIRC). I had initially assumed a stuck auto fill (I never did hear back on if that was the culprit), but since she is in close proximity to you, it now seems to me that maybe you guys got hit with some high CH water this summer. Maybe you could check with the water company and see if they can provide some insight (although they may not cop to it!).

That is just too high of a jump in too short of time (for both of you). And we've had such a mild summer that I'm not sure evaporation is completely to blame! Something weird is goin on in the OC!

 

[rhythm]

Thanks all for the replies...

salp, I have never done a full or partial drain of our pool, but it's only about 4 years old. I was planning on doing it some time between now and next Spring because the daily use of liquid chlorine over time has caused the sodium content to get to the point where we can taste it in the water now. So I guess I'll be taking care of two issues now, not just one!

paulr, yes I'm aware of the two different ways to carry out the test, but I've only done the 10ml sample for CH since I know that my CH will always be pretty high. I could try the 25ml sample method today (the magnetic stirrer will make it tolerable I guess). I could also try adding 5-6 drops of the R-0012 first, just to see if there is a floating endpoint issue that's messing up my test.

I hadn't thought about the calcium build up with evaporation (oops!). I guess I was thinking that my pool CH would always be pretty close to our tap water CH. And the more I think about it, it's probably been longer than I thought since I verified the 350-400 ppm range for our pool's CH, so I guess it could have come up this much since then. It seems like a lot to rise, but given what simicrintz said about that particular client's pool, it might be reasonable that mine doubled also.

In any case, it's time to replace some pool water! This would be a good time to do it too, given what I measured yesterday from our tap (200 ppm CH).

Thanks,
Greg

 

[Guest]

Greg,

You can always consider Reverse Osmosis instead of draining. Its a better solution.

 

[mamacrumbcake]

We did a pool not far from you (Dove Canyon) earlier this year, and took the CH under 200 (I can't remember exactly where) and she is already up to 450 (IIRC). I had initially assumed a stuck auto fill (I never did hear back on if that was the culprit), but since she is in close proximity to you, it now seems to me that maybe you guys got hit with some high CH water this summer. Maybe you could check with the water company and see if they can provide some insight (although they may not cop to it!).

Greetings from Dove Canyon! Yep, that's my pool--went from under 200 in May when we did the R/O to 650. I've been meaning to post but have been super busy. The water in the pool is perfect and very consistent--levels for salt, borates, cya, etc have not been fluctuating. It's only the CH, which has been rising over the summer. I'm baffled. Bruce mentioned the autofill. We do have an autofill and it seems to be working fine. I say "seems" because I have not found it yet. The previous owner said I'd have to go digging around under plantings; I think it is literally buried under dirt and shrubs. If anyone has any insight into why the CH would rise so fast, I would love to hear.

I use the TF100 Test Kit and test the CH according to these instructions from Taylor (see "Beware the Fading Endpoint," which is what I have)

http://www.taylortechnologies.com/Chemi ... ntentID=70

Our current test results are

Salt 3200
FC 6.0
CC 0
TC 6.0
pH 7.7
TA 70
CH 650
CYA 50
Borates 40

Thanks to everyone here at TFP, we have had a wonderful summer in the pool!

Karen

 

[dmanb2b]

If you have high CH fill water and your pool has a leak that is being masked by the autofill, that would certainly cause your CH to rise. It may be worth it for you to find the autofill shut-off and see if you have a leak

 

[Richard320]

It's not only possible, it's likely.

You've already covered most of what I have to offer, but let me just toss out my personal experience. I have astronomical CH. Recently I pumped out close to 10% of my water and refilled. CH dropped from 1150 to 975. The fill water was testing at 170, by the way. Over the next couple weeks, with not much water added, it crept up to 1000, then 1050, and so on. 3 weeks after the pumpout, it was back up to 1100. So more draining. Bizarre? Not at all - it was expected and hoped for. The calcium scaling on my walls is visibly less than it was 8 or 9 months ago when I started taking an interest in the water chemistry. In fact, the spa seats are almost a negative image of what they were. I want it to keep climbing so I can pump it out, and eventually perhaps do R/O. No point reducing the CH if it will just start dissolving the scale again and re-saturating!

I wouldn't be at all surprised if the same isn't happening to you. The calcium was crystalizing on the walls, and now that you've been maintaining pH and TA, it's starting to dissolve back into solution. Hence, super-high CH.

 

[Guest]

Some of Karen's high CH might be attributed to the scale Richard, but her pool looked pretty good overall. There was some scaling, but it was not what I would call excessive.

You do bring up a good point though. I wonder if there is a way to figure out (relatively speaking) how low we would have to go on the CH number to allow for the CH to come out of suspension? It would obviously be all over the board on guessing how much exists and how much would come off and how low we would go and how long it would take and how low to keep the pH to make it happen sooner.......... Whew; I need a comma or something in there!

We try to hit around 150-200 on the CH, but have gone as low as 50 before (we put calcium chloride back in to bring it back up ). That gives a fighting chance to allow for some to come back in suspension and not affect the total too quickly. My guess would be that there just isn't enough there to change the numbers dramatically, but I could be wrong.

 

[mamacrumbcake]

If you have high CH fill water and your pool has a leak that is being masked by the autofill, that would certainly cause your CH to rise. It may be worth it for you to find the autofill shut-off and see if you have a leak

Thank you. I was wondering about this as Bruce also suggested it to me. I don't understand how a leaking pool could contribute to a rise in CH (not saying that it wouldn't, just that I don't understand it). I was thinking the opposite might happen since high CH water leaks out and is refilled by lower CH water (our fill is 280). Also, if there were a leak in the pool, wouldn't I see the levels dropping for salt, borates, and cya? I'm thinking that the water that leaked out would contain those things but the new fill water would not.

 

[dmanb2b]

Yeah...that's likely not the cause then...not with fill CH at 280. Your thoughts are on point.

 

[mamacrumbcake]

I wouldn't be at all surprised if the same isn't happening to you. The calcium was crystalizing on the walls, and now that you've been maintaining pH and TA, it's starting to dissolve back into solution. Hence, super-high CH.

Hi Richard, when the CH started climbing, this was my first guess too. After we did the R/O, the CH was under 200 and the fill water was 280. Over time, we'd expect the CH to rise, but not this fast. Where else could the calcium come from? It really makes me wonder if it didn't just dissolve off of the walls of the pool.

 

[Guest]

I had a similar issue, two years after our pool was built. Into my third year, my CH was 900ppm. It jumped from 350ppm to 900ppm like overnight. I drained my pool by 1/3rd, CH was down to 650ppm and in three months it was back up to 900ppm. I just think we have days where tap CH is high, maybe like 500ppm or higher. I really cannot think of any other way that this happens. I live in North County San Diego. My water service is Rainbow Municipal and they have been doing all kinds of work the last three years on existing pipes and reservoirs. Since I have R/O'd my pool in December of last year. We dropped our calcium hardness to about 220ppm. As of this week, my CH was 320ppm.

Our water tables out west are really low from drought conditions, is it possible we are getting more calcified water due to water levels???