Just got Taylor K-2006C AND Sutro system

[pgershon]

Checking accuracy side by side and finally looking at my own pool. The Sutro seems to be reading in-line with Taylor test after 2 days of comparison. Taylor on pool reads pH and free chlorine and alkalinity correctly so far.

But I have some questions on my readings, and also some spots on my pool surface I cannot identify (see photo, pool is 10 year old Diamond Brite).

Pool (82 degrees) - about 30,000 gals:

Free chlorine 3.4 (combined 0.4)
pH 7.8 (2 drops acid demand)
Total Alkalinity 120
Calcium hardness 70
Cyanaric acid 70
Salt 3600

Spa (103 degrees) - about 200 gals:

Free chlorine 11.5
pH 8.0+ (3 drops acid demand)
Total Alkalinity 120
Calcium hardness 70
Cyanaric acid 0
Salt 3000

Next steps:

pH is running high in both pool and spa - worse in spa
Turning down spa chlorination level - its too high

Questions:
1) should I be concerned with the calcium hardness being so low in both pool and spa? Might this be a reason why I have lots of Diamond Brite dust coming off when I run my new pool Robot (the filters fill with blue and white sand-like residue). Seems like the surface plaster is coming deteriorating. Frustrating because I pay my pool company $350/week on average to maintain my pool and spa, and they seem to ignore. Quick note - my water comes from a well, but also runs through a water softening filtration system. That may explain low calcium.

2) how can I determine what the spots are in the pool. They seem to have gotten worse over last 10 days. I am attaching a photo of the shallow end (spots are the black dots - please ignore shadows and the patched cracks where the colors did not match). Spots are dark and very small - could be black algae but I am not sure why I'd suddenly get an outbreak with my chemistry pretty stable. Could be some kind of metal from well water also - I expected to see higher calcium. Ideas?

 

[Katodude]

Did you test CH with a 10ml or 25ml sample?

If your CH really is 70 that is too low for a plaster pool, and could explain what you are getting. Enter your numbers in pool math and see what your CSI is.

 

[pgershon]

Did you test CH with a 10ml or 25ml sample?

If your CH really is 70 that is too low for a plaster pool, and could explain what you are getting. Enter your numbers in pool math and see what your CSI is.

CSI is 0.51 - too low. I need to add calcium. And a lot of calcium. Probably because the pool is filled with water from softener. Bad that this had probably gone on for years - my pool walls are crumbling a bit and this must be why.

 

[Katodude]

You do need to add calcium, but not too much. Dont overshoot. Start with about 250 and then see. Your CSI is fine now but only because you pH is crazy high. Set you pH to 7.8and TA to 80 at what it should normally be and you will see you CSI is -0.4 which is pretty corrosive.

 

[jseyfert3]

Your pool pH is not high. In general unless you are battling a high pH you don’t need to lower the pH until it hits 8. Currently your CSI is -0.48 according to PoolMath. If you add enough calcium to get to 250 ppm then your CSI will be 0.07 with all other items as they are. I agree don’t add too much, you don’t want to swing the pendulum to the other side, just center it.

Probably because the pool is filled with water from softener.

That will mean the fill water has a CH of 0 if the softener is properly working. Some people fill from softeners to avoid CH buildup that often happens in dry climates, but NY isn’t dry. Between winter partial draining and draining for rain overfill the CH will likely stay in check pretty well without the softener. You could likely do away with the softener fill, or perhaps better yet is installing some valves so you can use either softened or unsoftened water going forward depending on what your pool levels are.

Have you ever measured your fill water TA and CH? It’s handy to know them. A softener won’t affect TA, so you can get that sample anywhere. If you can get an unsoftened sample for CH that would be useful to know as well.

 

[jseyfert3]

Also when using a SWCG the minimum FC for a CYA of 70 is 3, and the target is 5. Try to, we’ll, target a FC level of 5. If you go over some don’t worry, a little more won’t hurt anything either, at a CYA of 70 it’s safe to swim in up to 28 ppm of FC.

But the 3 in minimum is like the absolutely do not ever let it drop below this level.

 

[pgershon]

Your pool pH is not high. In general unless you are battling a high pH you don’t need to lower the pH until it hits 8. Currently your CSI is -0.48 according to PoolMath. If you add enough calcium to get to 250 ppm then your CSI will be 0.07 with all other items as they are. I agree don’t add too much, you don’t want to swing the pendulum to the other side, just center it.
View attachment 345474



That will mean the fill water has a CH of 0 if the softener is properly working. Some people fill from softeners to avoid CH buildup that often happens in dry climates, but NY isn’t dry. Between winter partial draining and draining for rain overfill the CH will likely stay in check pretty well without the softener. You could likely do away with the softener fill, or perhaps better yet is installing some valves so you can use either softened or unsoftened water going forward depending on what your pool levels are.

Have you ever measured your fill water TA and CH? It’s handy to know them. A softener won’t affect TA, so you can get that sample anywhere. If you can get an unsoftened sample for CH that would be useful to know as well.

The softener is there for metals from my well water. The pool gets the same treated water that goes to the house.

 

[pgershon]

Also when using a SWCG the minimum FC for a CYA of 70 is 3, and the target is 5. Try to, we’ll, target a FC level of 5. If you go over some don’t worry, a little more won’t hurt anything either, at a CYA of 70 it’s safe to swim in up to 28 ppm of FC.

But the 3 in minimum is like the absolutely do not ever let it drop below this level.

I am confused about the target FC level. The Hayward manual for the SWG says to target 1-3 as opposed to 3-5. Why the difference?

 

[jseyfert3]

I am confused about the target FC level. The Hayward manual for the SWG says to target 1-3 as opposed to 3-5. Why the difference?

The difference is that the pool industry as a whole does not understand the relationship between CYA and FC. Essentially, the more CYA, the more bound up the chlorine is, making it less effective. CYA is, however, important to avoid extreme loss of FC to UV light from the sun. Therefore the best thing to do is maintain the FC level at a fixed ratio of your CYA level. TFP has these levels nearly laid out in a chart for easy reference, or they are shown in the TFP PoolMath app.

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

These values were developed using chemical equilibrium equations (look for the Pool Water Chemistry sticky in the Deep End if you want to dig into that) as well as experience of thousands of TFP members. They work and work well. For liquid chlorine the target valves are a little higher, and before a pool party I usually take our pool to SLAM level of FC. For a CYA of 40, that was 16 ppm FC. You couldn’t tell there was chlorine in the water. We’ve had more than one guest ask us if there was chlorine in the pool because it can’t be detected short of a test kit on a well maintained pool!

 

[pgershon]

Well I added 45 lb Calcium Chloride to the pool and 5 lb to the spa. Also added CYN to the spa. And added muriatic acid to pool. Improved those levels, but something happened to my FC along the way - it went from 3.4 to zero. SWG seems to be working - I added 2 gallons of 12% liquid chlorine last night and will re-check reading today. This is what I got for pool before adding the liquid chlorine:

FC 0.6
Combine 0.2
pH 7.7
TA 109
CH 220
CYN 70
Salt 3600

Do you think I may have something eating my chlorine. or is my SWG acting up? (SWG reading 26.2 V and 6.98 Amp) Pool looks clear but pool guy this morning said I had algae on walls and brushed it.

 

[mknauss]

No reason to use the 25 ml water sample to test FC/CC. 10 ml sample, one heaping scoop of R0870, and each drop of R0871 to clear is 0.5 ppm FC.
That kind of FC loss if the SWCG was operating at a % generation and run time to add 3 or 4 ppm per day means something is growing. See what tonights test show.

 

[pgershon]

I am curious. At 24 hour runtime and 100% and 3600 salt, how much chlorine should I expect from T-15 AquaRite?

 

[mknauss]

how much chlorine should I expect from T-15 AquaRite?

Your SWCG will add 4.4 ppm FC to your pool volume each 24 hours.

 

[pgershon]

I am going to wait until the sun goes down to do a full set of readings, but I did a spot check of FC before I went swimming and it was down to 2.0, after I added 2 gallons of 12.5% liquid chlorine (1 gallon at 2 PM yesterday and 1 gallon at 7 AM today). Obviously something is growing despite extremely clear looking water. I did notice two things (see photos attached):

1) Pool cleaning company puts Pool Magic sponges in pool at the start of every month. They stay in skimmers until someone removes, but I examine and one looks like it may have something growing on it - see photo. I removed them all. I am not sure what the Pool Magic is supposed to do, but they do in in lieu of adding CYA (which I added myself).

2) I have a rock waterfall in the pool. Water runs from one of my returns to the rock and then drips into the pool. I have always known there is a bit of water loss at the rock, but I looked carefully and there is green algae blooming there too. It may be in contact with my pool water, although barely. I should probably find a way to stop the water loss (which results in standing water). Any thoughts on this? I have teh ability to turn the waterfall on or off and generally just run it while I am heating the pool (in conjunction with running the variable speed pump at higher speed).

Any thoughts most appreciated, and I will post my full chemistry tonight one the pool is not in full sun.

 

[pgershon]

Here are tonight's readings for pool and spa (additions made at 7 PM - with update at 11 PM for FC):

Pool (25,000 gal):
FC: 2.5 (10 at 11 PM after adding liquid chlorine at 7 PM and with pump/SWG running)
pH: 7.8
TA: 120
CH: 220
CYA: 55
Salt: 3600

Added 5 cups Muriatic acid
2 gallons 12.5% liquid chlorine

Spa (3000 gal):
FC: 9.5
pH: 8+
TA: 130
CH: 200
CYA: 50
Salt: 3000

Added 5 oz Muriatic acid

Will see what FC looks like at 11 PM and 7 AM

7 AM update:

FC 11
pH 7.8

Chlorine went up slightly overnight with SWG on. I have now shut off (wish I had last night). I am surprised pH staying high given the acid I added, but perhaps the liquid chlorine offset.

Thoughts?

1 PM update: FC 9(without SWG after 4 hours in sun)
5 PM update: FC 6 - very hot and sunny day but ...

 

[pgershon]

Thanks for your help @mknauss and others. Given my readings, it sounds like I have something organic but will confirm tonight by testing overnight chlorine loss with everything off.

I am trying to determine what I might be missing - I have not seen any green (although the pool guy said there was minimal algae of the pool walls - he brushed and added an unknown algicide). Water looks very clear. My son brought a 5 yer old floating pool mat into the pool to lie on for an hour - could that be contaminated? Or might the visible algae on my waterfall (which I believe is in standing water that does not run into the pool) be a contaminant? I am not sure how to get rid of that.

Is SLAM (including closing my pool to swimmers for a few days) my only option?

 

[mknauss]

What algaecide did your pool guy add? If ammonia based, that is eaten up by chlorine. If copper based, well, you don't want that.

You have a quality test kit. I would relieve the pool guy of their duties.

Any algae that is in contact with the pool water is an issue and needs to be addressed.

If you SLAM, you can still swim. As long as your can see the bottom of the pool (for safety reasons) and your FC is between minimum and SLAM level for your CYA.

 

[pgershon]

So I can swim despite very high chlorine? That is a big plus.

Any ideas how to deal with my waterfall rock? I could hose to get rid of visible algae and then pour raw bleach on it. Trick is to keep algae out of pool. Normally the water that run on rock is from pool with FC

 

[mknauss]

Waterfalls that retain water in them are a real problem for pool water chemistry. Thorough cleaning very often is needed or they create an algae harbor. Clean it as best you can.

 

[pgershon]

Had no free chlorine loss overnight. FC stayed at 5.5.

So FC went from 11 to 5.5 during day but no loss overnight. Daytime usage of 5.5 seems high, but it was bright and sunny here in nY and days are ver long right now and shade for my pool is minimal after 9 AM this time of year.

Questions - is 5.5 PPM of FC usage during the day especially high for long sunny summer day in NY, and is the usage higher because levels areall above the target FC for my CYN? CYN is 50-60 depending on subjective reading of the dot.