How often having to add salt?

[BowserB]

Got a call this am that the installers might be here this afternoon to install the IC40 I bought on 5/13--weather permitting. The weather here in southeast Texas has not been very permitting the last couple weeks. Wonderful if you like to watch your St. Augustine grass grow, but not so much for other outdoor activities. Yesterday was a nice break with all day clouds only. That said, I just got a short inquisition from my wife about the SWCG that may be installed today. She is so far unimpressed with the anticipated maintenance reduction we would see with this miracle device, as all she has seen so far (even before the installation) is that one more test has been added to my weekly routine, plus I've brought a lot of 40lb bags of Morton Pool Salt home from HEB and spent a lot of time dumping and brushing salt in the pool. As a side note, she was unable to detect that the water felt any different when the salt was at 3600ppm compared to before I started adding salt, and it tested at 1200ppm. OK that's the introduction to my question. Here's the question, is this normal without anything to consume the salt yet? All test results are from the Taylor K1766 kit, and when the numbers dropped, I retested.

5/4: 1200 ppm before I started adding salt, one bag at a time walking around the pool, then brushing any accumulations to spread for faster dissolving.
5/7: 1800 5/9: 2600 5/11: 2800 5/12 am: 3000 5/12 pm: 3600
5/14: 3600 5/21: 3200 5/24: 3000 5/27: 3600 6/1: 3400

I added about half a bag of salt after this morning's 3400ppm test result and turned the pump up to 2500rpm. I'll check again in a couple hours. The IC40 manual recommends 3600-4500ppm with 3600 being "ideal." Odd that the bottom of the range would be ideal. We have had a fair amount of rain, although not a lot of inches. 1" in a day has been common; some days less than that. Since May 7, I have not gone to HEB one time that didn't include a bag of salt in my purchase. And one trip a month already included a bag of potassium salt for the water softener, so once a month, I'm hauling 80 pounds of bulk chemicals in my 2000 Subaru.

So my wife, always supportive, never critical, says "It seems like you're having to do more maintenance than ever before, and the salt water thing isn't even installed yet!" I explained that "this is preparation and we've had a lot of rain. But later, yes, I'll still have one more weekly test than before, although I might not be doing a daily chlorine test after a couple weeks, if the chlorine level stabilizes, and yes I'll have to check for scaling probably once a month, and I'll probably have to clean the cell once in a while, possibly once a month." My wife is not impressed. Keep in mind, this is "her" swimming pool. I would have put that $55,000 plus annual operating expenses in a vacation fund.

So is this what I have to look forward to? Instead of pouring liquid chlorine into the pool every couple days, I'll have to buy a bag of salt once a week and add "clean the salt cell" to my monthly chores? So far this pool has added work and only reduced my grass cutting by about 750 square feet...while adding more edging.

 

[Texas Splash]

Once you add salt, it's in. Salt does not disappear unless you have a leak or purposefully let-out water. More than likely what you are seeing is varying salt test results. It can fluctuate by a few hundred ppm. The important thing is that you have the salt level in that happy-medium ballpark range. Once you turn on the SWG, if it's happy you're happy. The K-1766 helps you feel more confident should the SWG start showing faults for low/high salt. So as long as the salt doesn't start dropping a lot without explanation, all is good.

 

[BowserB]

Update. After adding salt, it's back to 3600, but it just started raining. Pool is already at the overflow drain, so any new water is both diluting the salt and running out into the storm drain.

 

[BowserB]

Splash, there in SA, you've had pretty much the same rain as we've had here in Katy (west of Houston on I-10). I can't tell for certain how much water we've had run out the overflow drain from the pool, as the drain out to the street also collects water from the pool decking and two roof downspouts. I've done the bucket test in the recent past to confirm only evaporation has lowered the water level. At one point, the water going out to the street was hard enough to blow the popup drain cover off the PVC drain pipe and send it 50 feet into the storm drain--but again, that included roof and decking runoff water.

I find it odd that Pentair's "ideal" level for salt is at the bottom of the recommended range of 3600-4500ppm. Makes me think 4000 would be a safer level to shoot for, since it seems more likely that salt level will drop from rain than increase from other causes, although higher salt content probably means greater corrosion to metal and faster deterioration of flagstone coping.

 

[mknauss]

I find it odd that Pentair's "ideal" level for salt is at the bottom of the recommended range of 3600-4500ppm.

In your area, keeping a higher salinity is a good idea as you get rain.

Here, the only time I add salt is when I drain part or all the pool water. Otherwise my salinity goes up over time due to the use of muriatic acid. I start my salinity at ~2900 ppm. Just above Low Salt for the SWCG.

 

[EmilyOTR]

I add salt is maybe toward the end of pool season after a season of backwashing and splash out and rain. I was adding salt more frequently my 1st season and because it was my 1st season I didn't know, but we had a small leak. since that was fixed after the initial opening I don't really add much.

 

[BowserB]

In your area, keeping a higher salinity is a good idea as you get rain.

Here, the only time I add salt is when I drain part or all the pool water. Otherwise my salinity goes up over time due to the use of muriatic acid. I start my salinity at ~2900 ppm. Just above Low Salt for the SWCG.

Thanks all. IC40 was installed yesterday. Small leak at a PVC joint--I should have cranked up the pump to high speed while the guy was still here. Or he should have suggested that to be sure there were no leaks, but he had "several more stops" after he left here. These guys are really busy, with a lot of people still getting damage from the Texas Freeze fixed, due to parts shortage and so many new pools thanks to Covid keeping people at home. My neighbor's new pool is getting plastered as I write this. Pool construction started in December.

New SWCG set up question. I guess from here I just measure FC every evening (or morning?) and see if it drops below, or stays above, my target of 6 ppm (currently at 9.5ppm according to Taylor DPD/R870 test...IC40 manual suggests "superchlorinate" in advance of installation.) Then adjusting run time and/or % to make changes until it is more or less stable at the target. I started out at 40% with my pump running 11 hours during the day (9a to 8p) and five hours overnight (midnight to 5am) at 1650rpm, which is about 25 gpm. The manual recommends 20-30 gpm. So that's 16 hours a day at 40%. With my setup, if you found the FC not adequate, would you run longer or a higher percent? Or, if you found it climbing, what would you adjust?

Marty, could you elaborate on muriatic acid, aka hydrochloric acid, increasing salinity? What chemical reaction is at work there? HCl doing something with sodium bicarbonate? It's 58 years since I took chemistry in high school! Thanks again for all you guys guiding me as I continue to pour money and time into that hole in my backyard.

 

[mknauss]

Marty, could you elaborate on muriatic acid, aka hydrochloric acid, increasing salinity?

For the X's and O's - I will call on Matt @JoyfulNoise

So that's 16 hours a day at 40%

That is adding 3 ppm FC to the water each day. A good start. If you need more, raise the %
Best time to test in your case would be in the evening I would think, after 8p.
Is there a specific reason you are running two sets of run times? Only reason is to skim. You should also see what RPM closes your flow switch, then add 100 rpm. See if that flow rate is sufficient to skim.

 

[duckcmmndr]

I have had to add some twice this year already....once when the water warmed up enough to turn on my SWG. I lost a lot over the winter with all the raining and a few backwashes that I did. I leave my pool open in the winter and keep the pump running and add chlorine manually. Then this spring we have had about 20 inches of rain and I have had to add it again. We got 2.56" of rain yesterday afternoon!

I suspect this will stop once the "non-stop" rain goes away.

 

[jmastron]

I have had to add some twice this year already....once when the water warmed up enough to turn on my SWG. I lost a lot over the winter with all the raining and a few backwashes that I did. I leave my pool open in the winter and keep the pump running and add chlorine manually. Then this spring we have had about 20 inches of rain and I have had to add it again. We got 2.56" of rain yesterday afternoon!

I suspect this will stop once the "non-stop" rain goes away.

That's a lot of rain! You can calculate the loss -- rough calculation of your surface area is ~1500 square feet, so an inch of rain adds 127 cubic inches or ~1000 gallons of water. If you start with 30,000 gallons at 3500ppm and add 2 inches/2000 gallons, that'll dilute to ~3300 ppm if I'm doing the math right. With a continuous overflow the math it's more complicated, but should be close. So you could indeed end up adding a bag of salt after major rainstorms. Having just added a few bags to start up my new SWCG, I used advice here and just dumped the water softener crystals in a pile in the shallow end and brushed the pile back and forth for 5 minutes or so until it was gone.

I have to drain manually (no autofill or overflow) so can track it a bit better. We get 18 inches of rain a year, but virtually none in the summer and otherwise spaced so I only have to drain off a few inches a year total (none this past drought winter)

Edit: Realized the quote wasn't from the OP, but the math works out the same since the surface and volume are both about half -- 18x39 is 700sf, or 440 gallons/inch. 2 inches of rain adds ~900 gallons to the 15,000, so similar dilution.

 

[mguzzy]

Bowser you can play with runtimes using the effects of adding section of the Pool Math App. Its nice for finding the middle of the road pump runtime so you can just adjust everything else by the % output. Remember your output will go up as you progress through the summer and then down as you approach fall. Its just a matter of tweaking the knob to fit the situation. In reality it will take a couple of seasons to really nail it down. Sounds like you get a LOOOOt of rain. So you'll have to factor that into your testing regime.. Once my summer starts I get no rain,,, so there is no dilution, and the salt stays where it is.

 

[sduda210]

I get about 40 inches of rain per year and I lose salt due to backwashing my sand filter. Seems like I go through 8 bags a year.

 

[JoyfulNoise]

Marty, could you elaborate on muriatic acid, aka hydrochloric acid, increasing salinity? What chemical reaction is at work there? HCl doing something with sodium bicarbonate? It's 58 years since I took chemistry in high school! Thanks again for all you guys guiding me as I continue to pour money and time into that hole in my backyard.

Every gallon of muriatic acid (31.45%) adds ~36ppm of chloride ions to 10,000 gallons of pool water. Hydrochloric acid is hydrogen chloride or HCl. When hydrogen chloride is added to water, it completely dissociates -

HCl ---> H⁺ + Cl^-

The hydrogen ion adds to the acidity of the water and lowers pH while the chloride ion adds to the measured "salt" level of the water. The K-1766 salt test kit measures chloride ion (Cl-) directly and then reports it's answer in units of NaCl concentration. Your SWG creates sanitizing chlorine from chloride ions.

 

[duckcmmndr]

Every gallon of muriatic acid (31.45%) adds ~36ppm of chloride ions to 10,000 gallons of pool water. Hydrochloric acid is hydrogen chloride or HCl. When hydrogen chloride is added to water, it completely dissociates -

HCl ---> H⁺ + Cl^-

The hydrogen ion adds to the acidity of the water and lowers pH while the chloride ion adds to the measured "salt" level of the water. The K-1766 salt test kit measures chloride ion (Cl-) directly and then reports it's answer in units of NaCl concentration. Your SWG creates sanitizing chlorine from chloride ions.

Nice Info!

 

[BowserB]

We have recently had a lot of rain. Until about three weeks ago, though, we were officially in drought condition. As of this morning, I understand that for this year so far we're exactly where we should be for June 2. Three weeks ago we were in a drought, and now we're "caught up," so yes we've had extraordinary rainfall recently. Just a few miles north of us, the rain has been quite a bit more.

Skimming. Our location about 50 miles from Galveston Bay and 55 miles from the Gulf of Mexico, gives us generally wind out of the south 80% of the time. That blows from the shallow end of the pool to the deep end where there is a skimmer. Second skimmer is on sort of the southeast corner. (In my little picture that's the top left.) As a rule, the north end skimmer gets 3 times as much stuff as the other one. As far as cleaning the surface of leaves, flying ants, and other stuff, I've found that around 1500 rpm is the lowest that moves stuff into the skimmer (where I have socks in both.) At 1500 rpm, the pump uses 180 watts and moves about 23 gpm of water. As to why I have two four hour off times, I can't really say. Just an old time notion that a machine can't run 24 hours a day nonstop and not self destruct, so I have it shut off 8 hours in two 4 hour segments.

Matt, thanks for the chemistry explanation. I don't know if others are interested, but it helps me to understand what is happening when one change affects something seemingly unrelated. For certain, no one in my house besides me cares! I had a hard time finding anyone to get excited about our nation's Mars mission having a successful test of a device to separate oxygen from carbon dioxide in the Martian atmosphere. Next, water from the polar ice cap, and we're ready to build a Mars station! Only a couple clicks away from science fiction becoming science.

A few minutes ago the FC was down to 9 from 9.5 yesterday, after a mostly sunny day. Still no CC's. I need to get the CYA up, as it's only at 50 after I used pucks in a floater for a month and also used up the small package of Clorox brand stabilizer. More on the way. I'll gradually get the CYA up to 70 and also let the FC drop to 6, then start adjusting percent and run time to maintain. My wife is still quite disappointed that this new machine isn't a magic bullet that will take care of our chlorine needs. I never claimed it would be. The only one-time solution would be six dump trucks and a Bobcat. ;-)

 

[kellyfair]

I just want to hop in to comment on the cleaning part of your question. Cleaning your salt cell in acid decreases it’s life span as you are also removing the coating that makes it work. So you definitely are NOT cleaning weekly or even monthly. I think even once a season is too much. If you find that you are getting build up, holler!

 

[BowserB]

I just want to hop in to comment on the cleaning part of your question. Cleaning your salt cell in acid decreases it’s life span as you are also removing the coating that makes it work. So you definitely are NOT cleaning weekly or even monthly. I think even once a season is too much. If you find that you are getting build up, holler!

Thanks, Kelly. I specifically had the cell installed vertically to as to minimize scale from settling calcium (don't know if that really helps here, but it makes a big difference in A/C evaporator coils, so ... can't hurt.) The Pentair manual specifically recommends just water spray to clean the cell and only if scale isn't removed, then the HCl solution. Oh, and Kelly, I probably holler enough already, so if I get scale, I'll just whisper, "Oh no. More low maintenance!"

General salt update. We had 3.5 inches of rain last night in Katy. Salt was down from 3600 to 3200. I added the half bag I had, and now it's 3400 and still below Pentair's recommended minimum/ideal of 3600, so it's back to HEB for a couple bags of salt, although the light on the cell indicates salt is OK. pH was also up. In the old days we used to have acid rain; now it's alkaline rain? Added muriatic acid and pH is back to 7.5.

I don't know about this concept of lower maintenance with a salt water chlorine chlorine generator. In the old days--that's 3 days ago--after a rain storm, I'd just go pour some liquid chlorine in the pool without measuring or testing...just add some chlorine and test later. Now I have to lug a bag of salt, add acid, and test asap to be sure I have sufficient salt and my pH is neither too high nor too low. Good thing I'm retired, or I might not have time for all this reduced maintenance!

 

[mguzzy]

Now I have to lug a bag of salt, add acid, and test asap to be sure I have sufficient salt and my pH is neither too high nor too low. Good thing I'm retired, or I might not have time for all this reduced maintenance!

Just like anything new, I think you are overthinking it. You will fall into a rhythm with your salt additions and there is quite a bit of a Salinity range they will work with. I don't think you nee to run out there as soon as the rain stops to add salt. Plus once your spring rains stop.. you won't be adding much if any (your spring rains do stop don't they?) Same with Acid.. I check that once a week. And there are other things you can do to help buffer that a bit (read up on Borax when you have time).

 

[JoyfulNoise]

I don't know about this concept of lower maintenance with a salt water chlorine chlorine generator. In the old days--that's 3 days ago--after a rain storm, I'd just go pour some liquid chlorine in the pool without measuring or testing...just add some chlorine and test later. Now I have to lug a bag of salt, add acid, and test asap to be sure I have sufficient salt and my pH is neither too high nor too low. Good thing I'm retired, or I might not have time for all this reduced maintenance!

You’re micromanaging your salt levels too much and placing too much emphasis on rain dilution. Unless you are draining down your pool before it rains, most of the rain water will exit out the wall drain (assuming you have one) and never really mix with the bulk of the pool water. Pool water has much higher TDS than rain water and so the two layers will remain separated unless there is a long period of homogenization using the pool pump. The pH of natural rain water (away from industrialized areas) tends to be in the mid 7's as water will absorb a small amount of CO2 from the atmosphere when droplets form giving the water droplet some alkalinity. If there are SOx or NOx compounds in the air (do you live near a refinery or large city?), then rain water will tend to be acidic. But either way, unless there is a very large amount of water exchange (pool water leaving the pool and freshwater entering the pool), your chemical levels are not going to shift that much. When it rains, you should run the pumps but not the chlorinator, for a while to allow the surface water to homogenize with the rest of the pool and then turn the SWG on. Or, if you have the controls to do it, pull all or most of your intake water from the main drain and run the pump and chlorinator.

SWG's, especially Pentair IntelliChlor's, are designed to operate in a salinity range that spans 2800ppm to 4500ppm. The FC output of the cell does not change with salinity if it is kept anywhere in that range. There is nothing magical or necessary in targeting 3600ppm. I ran my pool for years with the salt level at 3900 to 4100ppm initially and then, just this past season, I ran the SWG with a salinity of 2900ppm. So there is no reason to constantly add salt to the water. Simply wait until it becomes an issue and then add salt. You're simply giving yourself extra work.

 

[Newdude]

General salt update. We had 3.5 inches of rain last night in Katy. Salt was down from 3600 to 3200. I added the half bag I had, and now it's 3400 and still below Pentair's recommended minimum/ideal of 3600, so it's back to HEB for a couple bags of salt, although the light on the cell indicates salt is OK.

Listen to the little green light. This is one of the instances is bliss. If the cell is happy, so are you. Walk away not questioning it. Mine ran awesome at 2900-3K and I did my best to keep it there to minimize the *tiny* taste even further. Once or twice a season the red light would come on and I’d add a half a bag to shut it up.