Chemical Imbalance in Salt Water Pool

[Mike Conroy]

Hi. I live in southern Spain. I'm renting a villa with a salt water pool. There are no manuals and the landlord is very vague about how to maintain the pool.


I have an in ground salt water pool; with concrete sides & base and tiled surface; capacity = 65 c.m. (17k US gallons, 14.3k UK galllons).
The chlorinator is generic, labelled RP35 and, I believe, requires salt level of 4,500 ppm - 5,500 ppm.
Pump is ESPA Squiper 80M (max 15.8 cu.m. p.h.).
Filter has max capacity of 16.5 cu.m. p.h.

The landlord's plumber (the local pool expert) has been advising me but we're not really making any progress. His main concern has been to reduce the pH level first. So I'd like to ask people who know for some help please.

For the past month I've recorded the levels of the chemicals. They've fluctuated but the pH & Cl levels have never come down to the right sort of levels.
The pool has no CYA and my test kits only cover Cl, pH & salt levels.
Today the salt level is 4.6 (1450 ppm)
The pH is 8.0.
The Cl is off the scale.

Reading https://www.troublefreepool.com/content/138-water-balance-for-swg-saltwater-chlorine-generator I see that the correct salt level is the first thing to correct. To get the pool up to 4,500 ppm would require 375 lb (170 kg) of salt (or 235 lb / 105 kg) to raise to 3400 ppm. Either way this is a lot of salt and, before I add it, I want to be sure that my plan is correct - I don't want an expensive mess to sort out later.
There is no CYA in the pool so I guess that my next steps will be to adjust the SWG % setting to keep the FC level in the 4 - 6 range.
Then adjust the pH with the addition of muriatic acid to get that down to 7.2 - 7.8.

Thank you, in anticipation, for any assistance.

 

[PoolGate]

What test kit are you using? Accurate testing is the key to success with a pool. Most tests do not accurately measure salt levels. When I see 4.6 my thoughts are that is 4.6 parts per thousand, which is a correct salt level and equates to 4600 parts per million. Before you add any salt, make sure you are accurately testing salt. If you are not adding chlorine then you have enough salt as no salt generator will work at a level that low. pH of 8 is not too bad you can get that down with a bit of Muriatic acid but again, accurate pH testing is key. Please put your pool specs in your sig line!

 

[Richard320]

If your FC level is that high, you have enough salt. The SWG wouldn't work that well otherwise.

pH is easy to fix, using acid. I have no idea what is and isn't allowed in the EU, so if Muriatic Acid is unavailable, use the dry acid. But if you have a choice, use MA.

I find it hard to believe your FC level maintains that high without CYA. Is the pool indoors?

I know test kits are a PITA to find in Europe, but I hope you aren't relying on test strips.

 

[Mike Conroy]

Thank you

For the salt level I am using Aquachek Test strips. According to the chart on the container a reading of 4.6 equates to 1450 ppm of salt.

As for the pH I'm using a test kit similar to Analysis of Water Pool - Swimming Pool Water Test Kit - jardiboutique: Amazon.co.uk: Garden Outdoors. Since 23 April I've added about 15 litres of acid with little change in the test results.

I could not see anywhere in my profile to add the pool specs?

Mike

- - - Updated - - -

Thanks.

The pool is outdoors.

I've checked with a couple of friends and they don't use CYA either.

The control panel for the chlorinator is also saying that salt levels are low.

I am using test strips. And, you're right, anything more sophisticated is very hard to find here!

M

 

[PoolGate]

Thank you

For the salt level I am using Aquachek Test strips. According to the chart on the container a reading of 4.6 equates to 1450 ppm of salt.

As for the pH I'm using a test kit similar to Analysis of Water Pool - Swimming Pool Water Test Kit - jardiboutique: Amazon.co.uk: Garden Outdoors. Since 23 April I've added about 15 litres of acid with little change in the test results.

I could not see anywhere in my profile to add the pool specs?

Mike

- - - Updated - - -

Thanks.

The pool is outdoors.

I've checked with a couple of friends and they don't use CYA either.

The control panel for the chlorinator is also saying that salt levels are low.

I am using test strips. And, you're right, anything more sophisticated is very hard to find here!

M

What is the scale for the test results on your strips (low and high)? I suspect that is wrong and it is 4600 ppm and not 1450 ppm.

 

[Richard320]

Thank you

For the salt level I am using Aquachek Test strips. According to the chart on the container a reading of 4.6 equates to 1450 ppm of salt.

As for the pH I'm using a test kit similar to Analysis of Water Pool - Swimming Pool Water Test Kit - jardiboutique: Amazon.co.uk: Garden Outdoors. Since 23 April I've added about 15 litres of acid with little change in the test results.

I could not see anywhere in my profile to add the pool specs?

Mike

- - - Updated - - -

Thanks.

The pool is outdoors.

I've checked with a couple of friends and they don't use CYA either.

The control panel for the chlorinator is also saying that salt levels are low.

I am using test strips. And, you're right, anything more sophisticated is very hard to find here!

M

A thought: your pH test my be falsely high due to the high chlorine. You say it's 8. That kit looks like it uses OTO. Personally, I can't tell the difference between 3 and 5 on those. What you see as 8 could well be even higher, and we know that Taylor reagents react with high FC and give a falsely high reading. Check out the pictures: Accurate pH test during shock levels with R-007? Yours probably does, too. They all use phenol red.

Maybe it's time to unplug the SWG and let the FC levels drop and then check things. If you've been running 8+ FC and no CYA for any length of time, you know there isn't any algae in there to explode into life when the FC dips! |

Click the My Profile link (right below poolschool link above) and then the About me tab to fill out signature.

 

[Mike Conroy]

If your FC level is that high, you have enough salt. The SWG wouldn't work that well otherwise.

pH is easy to fix, using acid. I have no idea what is and isn't allowed in the EU, so if Muriatic Acid is unavailable, use the dry acid. But if you have a choice, use MA.

I find it hard to believe your FC level maintains that high without CYA. Is the pool indoors?

I know test kits are a PITA to find in Europe, but I hope you aren't relying on test strips.

Thanks.

The pool is outdoors.

I've checked with a couple of friends and they don't use CYA either.

The control panel for the chlorinator is also saying that salt levels are low.

I am using test strips. And, you're right, anything more sophisticated is very hard to find here!

M

- - - Updated - - -

Apologies

I've not posted on forums for a while.

I've ended up replying multiple times.

I think I've got the hang of it now.

M

 

[Mike Conroy]

A thought: your pH test my be falsely high due to the high chlorine. You say it's 8. That kit looks like it uses OTO. Personally, I can't tell the difference between 3 and 5 on those. What you see as 8 could well be even higher, and we know that Taylor reagents react with high FC and give a falsely high reading. Check out the pictures: Accurate pH test during shock levels with R-007? Yours probably does, too. They all use phenol red.

Maybe it's time to unplug the SWG and let the FC levels drop and then check things. If you've been running 8+ FC and no CYA for any length of time, you know there isn't any algae in there to explode into life when the FC dips! |

Click the My Profile link (right below poolschool link above) and then the About me tab to fill out signature.

Thank you Richard

That was an interesting link you attached.

Tbh I couldn't follow all the detail but I get it that the pH readings, using phenol, can be false if Cl levels are high.

I will do as you suggest and switch off the SWG for a while. That should encourage the CL level to go down?

What is your thinking on the salt level which both my testing strips and the control panel suggest is low?

I'll put the pool details in as you suggest.

Thanks

 

[Richard320]

I don't run a SWG, personally. Someone else will have to tackle the salt level issue. But obviously there's enough salt for the thing to work.

Yes, shutting it off, turning it down, unplugging it, whatever, should see the FC level drop rather dramatically in a day. Without CYA, the half-life of chlorine is less than an hour. See the second graph here: Pool Water Chemistry

 

[mknauss]

If the pool has no CYA and is in any direct sunlight the FC will burn off very quickly.

The pool water really needs some CYA in it. It allows your SWCG to not run so much and also is much more comfortable to swim in.

 

[Mike Conroy]

If the pool has no CYA and is in any direct sunlight the FC will burn off very quickly.

The pool water really needs some CYA in it. It allows your SWCG to not run so much and also is much more comfortable to swim in.

Thank you again.

I have switched off the SWG and will wait to see what happens.

I did do this for 3 (sunny) days last week and, by the third day, the Cl had dropped from 3.0 - 6.0 to 2.0 - 4.0.

The pH level during this time was unchanged despite the addition of 3.5 litres of 24% solution HCl. That's the strongest concentration I can get locally, maybe I need to travel and get some more concentrated acid?

I'll look into adding CYA.

Mike

 

[Richard320]

Thank you again.

I have switched off the SWG and will wait to see what happens.

I did do this for 3 (sunny) days last week and, by the third day, the Cl had dropped from 3.0 - 6.0 to 2.0 - 4.0.

The pH level during this time was unchanged despite the addition of 3.5 litres of 24% solution HCl. That's the strongest concentration I can get locally, maybe I need to travel and get some more concentrated acid?

I'll look into adding CYA.

Mike

I'll bet your comparator block is marked CL-BR.

If so, the first number is the chlorine, the second would be bromine. Since you aren't using bromine (more a hot tub thing), ignore the second number. That being said, if it took 3 days for FC to drop from 3 to 2, you must have some CYA. That kind of loss would be expected in an hour without CYA, not over three days.

If you can't find a better test kit, maybe it's time to haul a sample to a pool store and have them check CYA. The pH and FC will be changed by a lengthy car ride, but the CYA results will be valid. That's the one I'm worried about.

Also, 24% acid is not bad. The full-strength stuff in the US is only 31%, and a whole bunch of people can only get the low-fuming stuff which is more like 16%.

 

[Mike Conroy]

I'll bet your comparator block is marked CL-BR.

If so, the first number is the chlorine, the second would be bromine. Since you aren't using bromine (more a hot tub thing), ignore the second number. That being said, if it took 3 days for FC to drop from 3 to 2, you must have some CYA. That kind of loss would be expected in an hour without CYA, not over three days.

If you can't find a better test kit, maybe it's time to haul a sample to a pool store and have them check CYA. The pH and FC will be changed by a lengthy car ride, but the CYA results will be valid. That's the one I'm worried about.

Also, 24% acid is not bad. The full-strength stuff in the US is only 31%, and a whole bunch of people can only get the low-fuming stuff which is more like 16%.

Thanks Richard

I think I'll wait a few days and see the outcome of switching off the SWG again. Perhaps I need to give it more time.......

I wonder if i should put more HCl in now, or wait to do that.

Thank you for all help!

 

[Richard320]

Thanks Richard

I think I'll wait a few days and see the outcome of switching off the SWG again. Perhaps I need to give it more time.......

I wonder if i should put more HCl in now, or wait to do that.

Thank you for all help!

Wait. The whole point in shutting it down is to get FC low enough that you can be sure the pH test is right. You don't want to add acid now and find out in a couple days that you now need to add stuff to raise pH.

 

[Dodger]

What is the scale for the test results on your strips (low and high)? I suspect that is wrong and it is 4600 ppm and not 1450 ppm.

The Aquacheck salt test strips have a translation scale. 4.6 => 1450ppm sounds about right. I no longer have the bottle, but my test notes show a reading of 6.4 => 3130ppm, and 6.6 => 3400ppm.

I used those strips for awhile and found them to have some repeatability errors. And, of course, the margin of error is quite large with that scale.
I assume OP's water temp in southern Spain at this time of year is not below 60 degrees. I found water temp affected both the strip reading and my SWCG control panel reading quite a bit.

 

[Mike Conroy]

Wait. The whole point in shutting it down is to get FC low enough that you can be sure the pH test is right. You don't want to add acid now and find out in a couple days that you now need to add stuff to raise pH.

Yes, of course. I'll wait & see what happens. Last time I switched the SWG off for 3 days the FC dropped to 2; however the pH was unchanged at 8. The sun is getting stronger though so.......Thanks again

 

[Mike Conroy]

The Aquacheck salt test strips have a translation scale. 4.6 => 1450ppm sounds about right. I no longer have the bottle, but my test notes show a reading of 6.4 => 3130ppm, and 6.6 => 3400ppm.

I used those strips for awhile and found them to have some repeatability errors. And, of course, the margin of error is quite large with that scale.
I assume OP's water temp in southern Spain at this time of year is not below 60 degrees. I found water temp affected both the strip reading and my SWCG control panel reading quite a bit.

The air temperature is 75 degrees atm. Should I buy a thermometer to check the pool temp?

A reading of 6.6 does equate to 3400 ppm. Should I start adding salt gradually to get the reading up to that level.

I've read on a couple of sites that the chlorinator will not function properly unless the salt is at that level or higher. I don't know if this is true nor do I know what they mean by "not work properly".

Both my FC (off the scale) and my pH (8) are consistently high.

Thank you

 

[Dodger]

The air temperature is 75 degrees atm. Should I buy a thermometer to check the pool temp?

A reading of 6.6 does equate to 3400 ppm. Should I start adding salt gradually to get the reading up to that level.

My main point about the strips was to verify your conversion scale.

But also that they are not very precise and have quite a bit of error with lower water temps. So don't add salt just because of the Aquachek reading you are getting. Your other data points (like really high FC) are not pointing to needing salt. But the water chemistry guys like Marty and Richard are better advisers on that.

BTW, your SWCG may have a water temp readout somewhere.

 

[mknauss]

If the 'off the scale' FC is a real reading, then your SWCG must be generating or you are adding chlorine through another source.

To lower pH you must add acid. You said you had added 15L so far. What strength?