Hydrochloric Acid vs Sulphuric Acid in automated dosing

[fanis.merk]

Hello,

I have been reading all the materials on this site and finding it to be immensely helpful. I also read the sections and forum posts related to Hydrochloric Acid (HCl) vs Sulphuric Acid (H2SO4). I understand that Hydrochloric Acid is quite a natural choice from a chemical perspective as it doesn't introduce additional sulphates.

However in Europe there are other practical issues that need to be taken into consideration. First of all land plots in Europe are smaller in comparison to the ones in US. Most of us have concrete pools and our water and acid pumps, SWG are all underground in a concrete closed room as opposed to an open air section behind a separator in US (at least it is what I see in youtube videos). HCl is more prone to fumes so this is an issue that needs to be evaluated in a closed room with poor ventilation.

Secondly, major acid pump producers caution against usage of HCl. I gathered below the manuals from 5 different acid pumps (one of them is in Spanish but same story).

https://beniferro.eu/wp-content/uploads/2021/09/Quickstart-Pool-Duo-HS-EN.pdf
https://www.amazon.de/-/en/Peristaltic-dosing-proportional-dosage-measurement/dp/B07PGKTKBT
BOMBA DOSEADORA POOL EASY - pH / Redox
Pool pH Dosing Pump
https://www.distripool.fr/medias/notice_technique/00.008.374_UM Micro Astral_rev1 (1).pdf

I also directly talked to a company that produces peristaltic pumps, they told me that hose damage is common when used with HCl.

In US there seems to be at least two producers, Hayward and Pentair, who seem to produce more amenable pumps. But they also emphasize the dilution of HCL to 16%, which is not a standard product around here so needs more handling from the pool owner's side.

https://www.hayward-pool.com.au/ass.../manuals/AQR-pH-upgrade-kit-owners-manual.pdf
https://www.hayward-pool.com.au/ass...ia/pdf/manuals/omnilogic-chem-pump-manual.pdf

Moreover it seems they need frequent maintenance as discussed on this site as well.

Pentair Intelliph - Further Reading

There seems to be more issues that need to be taken into consideration than the chemical simplicity of HCl. I have been dosing my pool automatically with H2SO4 (as described in Astral Micro PH manual, link above) for the last 2 years without any technical problems. Yes I have Calcium Sulphate accumulation in my pool as my water has 650 calcium hardness. But it is not really a showstopper. We also tend to replace the water every summer season. Pools are rarely kept operational during winter as it is cheaper to clean it beginning of summer than paying the electricity bill over the winter.

I really would like to switch to HCl to get rid of the swimming sulphates and better protect my SWG. My question is what I should do? Is it for example feasible to drill an exhaust pipe from HCl container that will carry the fumes outside of the pump room? Can I find a hose that is more durable to HCL? In general most pool owners just want to be pool enjoyers than pool masters (although it doesn't hurt to be one). Even though I learned all the inns and outs from this site, I am not sure if I want to disassemble my acid pump every year. Also when I am not around someone less capable needs to dilute the HCl. Currently our process is as simple as just dipping the hose from an empty container to a full one and tightening the lid. Or should I forget about this altogether?

Thanks

 

[Bperry]

Hello,

I have been reading all the materials on this site and finding it to be immensely helpful. I also read the sections and forum posts related to Hydrochloric Acid (HCl) vs Sulphuric Acid (H2SO4). I understand that Hydrochloric Acid is quite a natural choice from a chemical perspective as it doesn't introduce additional sulphates.

However in Europe there are other practical issues that need to be taken into consideration. First of all land plots in Europe are smaller in comparison to the ones in US. Most of us have concrete pools and our water and acid pumps, SWG are all underground in a concrete closed room as opposed to an open air section behind a separator in US (at least it is what I see in youtube videos). HCl is more prone to fumes so this is an issue that needs to be evaluated in a closed room with poor ventilation.

Secondly, major acid pump producers caution against usage of HCl. I gathered below the manuals from 5 different acid pumps (one of them is in Spanish but same story).

https://beniferro.eu/wp-content/uploads/2021/09/Quickstart-Pool-Duo-HS-EN.pdf
https://www.amazon.de/-/en/Peristaltic-dosing-proportional-dosage-measurement/dp/B07PGKTKBT
BOMBA DOSEADORA POOL EASY - pH / Redox
Pool pH Dosing Pump
https://www.distripool.fr/medias/notice_technique/00.008.374_UM Micro Astral_rev1 (1).pdf

I also directly talked to a company that produces peristaltic pumps, they told me that hose damage is common when used with HCl.

In US there seems to be at least two producers, Hayward and Pentair, who seem to produce more amenable pumps. But they also emphasize the dilution of HCL to 16%, which is not a standard product around here so needs more handling from the pool owner's side.

https://www.hayward-pool.com.au/ass.../manuals/AQR-pH-upgrade-kit-owners-manual.pdf
https://www.hayward-pool.com.au/ass...ia/pdf/manuals/omnilogic-chem-pump-manual.pdf

Moreover it seems they need frequent maintenance as discussed on this site as well.

Pentair Intelliph - Further Reading

There seems to be more issues that need to be taken into consideration than the chemical simplicity of HCl. I have been dosing my pool automatically with H2SO4 (as described in Astral Micro PH manual, link above) for the last 2 years without any technical problems. Yes I have Calcium Sulphate accumulation in my pool as my water has 650 calcium hardness. But it is not really a showstopper. We also tend to replace the water every summer season. Pools are rarely kept operational during winter as it is cheaper to clean it beginning of summer than paying the electricity bill over the winter.

I really would like to switch to HCl to get rid of the swimming sulphates and better protect my SWG. My question is what I should do? Is it for example feasible to drill an exhaust pipe from HCl container that will carry the fumes outside of the pump room? Can I find a hose that is more durable to HCL? In general most pool owners just want to be pool enjoyers than pool masters (although it doesn't hurt to be one). Even though I learned all the inns and outs from this site, I am not sure if I want to disassemble my acid pump every year. Also when I am not around someone less capable needs to dilute the HCl. Currently our process is as simple as just dipping the hose from an empty container to a full one and tightening the lid. Or should I forget about this altogether?

Thanks

Is there a reason you can’t dose acid manually?

 

[fanis.merk]

Is there a reason you can’t dose acid manually?

When you have a SWG your pH slowly creeps higher. Automated dosing makes things so easy that I would never go back to manual dosing. Once you balance your chemistry you rarely need to anything but enjoy your pool. It is such a big convenience. All I do is send the robot from time to time for surface cleaning. Everything else is on autopilot.

 

[Newdude]

When you have a SWG your pH slowly creeps higher.

We've found that lowering the TA to 60 and maintaining a Ph in the high 7s helps mitigate the rise substantially. Many times people are still chasing the high range of TA and low range of Ph that the industry reccomends.

 

[mknauss]

When you have a SWG your pH slowly creeps higher.

You have an overflow pool. The aeration is the issue. The SWCG does not increase your pH.
Lower your TA and the pH rise will slow dramatically.
What is your fill water TA and how much fill water do you use?

 

[fanis.merk]

We've found that lowering the TA to 60 and maintaining a Ph in the high 7s helps mitigate the rise substantially. Many times people are still chasing the high range of TA and low range of Ph that the industry reccomends.

Yes my TA is 50 and pH is locked at 7.5 with my pH automation probe. I still I consume around 5 gallons of H2SO4 per month. I read all the lessons and threads on this site.

 

[fanis.merk]

You have an overflow pool. The aeration is the issue. The SWCG does not increase your pH.
Lower your TA and the pH rise will slow dramatically.
What is your fill water TA and how much fill water do you use?

I already have TA at 50. See my other answer. My fillwater has 300 TA and 650 CH. That’s why when I open the pool for the season I smack the TA down to 50 first. I think I have roughly 250-500 liters of daily evaporation as temperatures are 38-40 Celsius in summer.

 

[mknauss]

250-500 liters of daily evaporation

That drives your pH rise.

 

[fanis.merk]

That drives your pH rise.

Possible but fill water is 7.4 pH even though it has 300 TA and I keep the pool at 7.5. So I am not filling with a higher pH than my pool and I cannot do much about evaporation.

 

[Bperry]

When you have a SWG your pH slowly creeps higher. Automated dosing makes things so easy that I would never go back to manual dosing. Once you balance your chemistry you rarely need to anything but enjoy your pool. It is such a big convenience. All I do is send the robot from time to time for surface cleaning. Everything else is on autopilot.

There are people in the US with acid dosing systems that use the HCL, so not smart enough to know the difference in the systems over there in why they can’t do it. Have you considered CO2 injection and getting rid of acid altogether?

 

[mknauss]

Possible but fill water is 7.4 pH even though it has 300 TA and I keep the pool at 7.5. So I am not filling with a higher pH than my pool and I cannot do much about evaporation.

The pH of the fill water is not a big driver. The TA is.

 

[fanis.merk]

The pH of the fill water is not a big driver. The TA is.

I understand but these are the conditions I have. What is your recommendation?

 

[fanis.merk]

There are people in the US with acid dosing systems that use the HCL, so not smart enough to know the difference in the systems over there in why they can’t do it. Have you considered CO2 injection and getting rid of acid altogether?

There is not much feedback from people on this site who actually use automated HCl dosing. The article on this site recommends yearly hose replacement. So there actually seems to be some truth to difficulties in pumping HCl even though chemically it is a better solution. I will look into CO2 injection systems. So far never heard of them in the market but I understand how it works.

 

[mknauss]

None. Just that I needed to document that the SWCG does not raise the pH of your pool water. That is a myth that is widely circulated. The pH rise of your pool water is due to adding high TA fill water and the aeration caused by having an overflow style pool.

Be ware of using CO2. As your fill water TA is high, the CO2 does not effect TA. Only the addition of acid does that. You would still need to add acid to control the TA rise.

 

[Bperry]

There is not much feedback from people on this site who actually use automated HCl dosing. The article on this site recommends yearly hose replacement. So there actually seems to be some truth to difficulties in pumping HCl even though chemically it is a better solution. I will look into CO2 injection systems. So far never heard of them in the market but I understand how it works.

The injection systems are somewhat pricy and so I suspect most people just manually add acid once in a while. I’ve read about a few of them though. The CO2 systems have been reviewed a few times here.

 

[fanis.merk]

None. Just that I needed to document that the SWCG does not raise the pH of your pool water. That is a myth that is widely circulated. The pH rise of your pool water is due to adding high TA fill water and the aeration caused by having an overflow style pool.

Be ware of using CO2. As your fill water TA is high, the CO2 does not effect TA. Only the addition of acid does that. You would still need to add acid to control the TA rise.

Thanks. It seems I am stuck with what I have. I was thinking to take a risk and try pumping highly diluted HCl with my pump next season. I hope someone will come up with a recommendation by then.

 

[scottts]

There is not much feedback from people on this site who actually use automated HCl dosing. The article on this site recommends yearly hose replacement. So there actually seems to be some truth to difficulties in pumping HCl even though chemically it is a better solution. I will look into CO2 injection systems. So far never heard of them in the market but I understand how it works.

Here's some feedback on HCL dosing.

I've been dosing 14.5% HCL using a pentair intellichem system for over 3 years. The only maintenance I've had to do is replace the peristaltic tube last year. I should have replaced it at the 2 year mark. Took under 5 minutes to change it. The Pentair system (made by Stenner I think) is extremely easy to maintain.

My fill water is TA about 120, CH about 220. I can evaporate something like 800 gallons per week in summer months.

I know the mantra here is that an SWG doesn't raise pH, and perhaps that's true when the entire chemical cycle is considered, but the fact is my pH rises when the SWG is on and acid needs to be injected to maintain pH stable. I'm particularly in need of stable pH because I use ORP as a surrogate for FC and large pH changes make that difficult. I also have very high CH 1300+ in my pool right now and 90+ degree water so I can't afford the pH to rise above 7.2 or so to keep CSI in the negative. Consistent auto-dosing acid is extremely effective at keeping TA low (mine is 40) which also really helps reduce scaling of the SWG.

 

[fanis.merk]

Here's some feedback on HCL dosing.

I've been dosing 14.5% HCL using a pentair intellichem system for over 3 years. The only maintenance I've had to do is replace the peristaltic tube last year. I should have replaced it at the 2 year mark. Took under 5 minutes to change it. The Pentair system (made by Stenner I think) is extremely easy to maintain.

My fill water is TA about 120, CH about 220. I can evaporate something like 800 gallons per week in summer months.

I know the mantra here is that an SWG doesn't raise pH, and perhaps that's true when the entire chemical cycle is considered, but the fact is my pH rises when the SWG is on and acid needs to be injected to maintain pH stable. I'm particularly in need of stable pH because I use ORP as a surrogate for FC and large pH changes make that difficult. I also have very high CH 1300+ in my pool right now and 90+ degree water so I can't afford the pH to rise above 7.2 or so to keep CSI in the negative. Consistent auto-dosing acid is extremely effective at keeping TA low (mine is 40) which also really helps reduce scaling of the SWG.

Great feedback. I think I can replace the tube every three years. My poolwater is around 30-31 Celsius. Even though I don’t have ORP I truly enjoy my SWG and acid dosing. My question to you is whether you keep the HCl tank outdoors or indoors, and how you do ventilation.

 

[JoyfulNoise]

There are other considerations when it comes to acid dosing as sulfuric acid is extremely dangerous compared to hydrochloric acid. Sulfuric acid, even in a diluted state can cause rapid skin burns due to the nature of the bisulfate anion. By contrast, HCl is much safer since the chloride anion is not reactive. You can get a splash of HCl on your skin and easily rinse it off without incidence. A splash of sulfuric acid on your skin can easily result in chemical burns. For this reason, sulfuric acid in the US is a much more controlled and regulated substance and almost all of the equipment manufacturers will not allow its use. It is more of a commercial/industrial chemical. Acidic fumes are an issue with HCl but only when it’s concentrated up to 20 Baumé. Lower concentrations do not fume much at all. In the US there are both 31.45% and 15% HCl formulations easily available. Using 15% causes a lot less wear and tear on tubing.

All that said, you do not live in the USA and so you have to use what is most easily available to you in your local market. The replacement tubing should be easy to get and so if you can switch to HCl that’s a better choice from a chemical safety standpoint. But you do need to ensure good ventilation and I would be very cautious in storing the tank in a closed environment. You can add a vent fan and duct work but that can cost a lot of money if you have to penetrate walls.

Can you store the acid tank outside and just run the tubing to where the equipment is?

 

[fanis.merk]

There are other considerations when it comes to acid dosing as sulfuric acid is extremely dangerous compared to hydrochloric acid. Sulfuric acid, even in a diluted state can cause rapid skin burns due to the nature of the bisulfate anion. By contrast, HCl is much safer since the chloride anion is not reactive. You can get a splash of HCl on your skin and easily rinse it off without incidence. A splash of sulfuric acid on your skin can easily result in chemical burns. For this reason, sulfuric acid in the US is a much more controlled and regulated substance and almost all of the equipment manufacturers will not allow its use. It is more of a commercial/industrial chemical. Acidic fumes are an issue with HCl but only when it’s concentrated up to 20 Baumé. Lower concentrations do not fume much at all. In the US there are both 31.45% and 15% HCl formulations easily available. Using 15% causes a lot less wear and tear on tubing.

All that said, you do not live in the USA and so you have to use what is most easily available to you in your local market. The replacement tubing should be easy to get and so if you can switch to HCl that’s a better choice from a chemical safety standpoint. But you do need to ensure good ventilation and I would be very cautious in storing the tank in a closed environment. You can add a vent fan and duct work but that can cost a lot of money if you have to penetrate walls.

Can you store the acid tank outside and just run the tubing to where the equipment is?

I understand. The current setup doesn’t require us to poor acid at all. We buy 25kg containers and all we do is move the suction from empty container to the new container by moving the lid together with the hose (the hose goes through the lid). We have no splashes of acid.

HCl is also available in similar containers. The pump room is underground with a trapdoor. If I move the acid container outside it will be above the dosing pump level. Probably won’t work. Also it has max 8 feet of suction length by design. And it will also put the acid tank easily accessible to the kids. How much fuming should I expect from a closed lid container with the tube tightly going through the lid?