Hydrochloric Acid vs Sulphuric Acid in automated dosing

[fanis.merk]

FWIW, I dose Muriatic Acid in my pool using a Stenner pump (adjustable flow rate that I can dial in, as need be). Like you (@fanis.merk ) I have high TA fill/auto-fill water of 330. So it's a massive pain to manually dose MA. You get the yo-yo effect constantly (pH goes up, manually dose, pH goes down, pH goes up, dose, pH is back down, etc.), this is especially true with high evap pools (mine has a huge surface area compared to most and I have tons of water features that cause evap as well) because your auto-filling more 300-330 TA constantly. I got sick and tired of manually dosing 3-4x per week. So that's why I did a Stenner pump for it, (injection is after my heater and after my (2) SWCG's). Furthermore, I feel it's safer (for me), and I don't have to worry about getting acid on my patio/pavers anymore either as I walked around the pool for manual dosing. My Stenner pump is outside, and I can't speak to using the acid indoors, but I would imagine, that -could- be a big concern if you're not wearing a mask and there's no ventilation in the room. When I'm outdoors, I just have to make sure the wind doesn't kick the fumes back to me, but in 3 months of filling my Stenner pump, I have never had an issue with intake of the fumes, whereas when I would manually dose, at least once a week I'd inhale some no matter how cautious I was being.

Your situation in Europe is much different than mine in the US , but for my $.02, I would never go back to manually dosing MA (I can use up to 2 gallons per week, if I'm using my water features). Open to answering questions if you have any.

The problem is not the fumes while you are pouring the HCl in a tank. The problem is those fumes destroying all the equipment and metal in my technical room. Closed technical rooms are very common around here to keep things safe from rain, rodents and keep children safe.

Anyhow 3 months is too early for reliability. Many people on youtube complained about tube failure in HCl pumps after 1 year. If it is easily replaceable as the other poster mentioned it is not a big deal.

A bigger deal for me is the need to fill special tanks (i.e. airtight Pentair tank) from delivered acid containers. In our current setup we simply dip the hose in the newly delivered acid container. Anyone can do it in my absence. Doesn’t require any protective gear.

Anyhow. It seems HCl is not an option in my setup. Maybe in the future if I do a remodeling I can make a separate acid room with a large tank.

 

[scottts]

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.

My entire system, including the acid tank, is outdoors so no fume issues. Using the 14.5% acid follows Pentair's recommendations and reduces odor, but acid in an unventilated space is a recipe for corrosion of everything metal nearby.

 

[oldprophet]

My entire system, including the acid tank, is outdoors so no fume issues. Using the 14.5% acid follows Pentair's recommendations and reduces odor, but acid in an unventilated space is a recipe for corrosion of everything metal nearby.

Here we would dilute the acid with water. The feeder would run longer but the fumes and injury issues would be less

 

[xDom]

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.

I didn’t realise a lower TA contributed to a slower pH rise.
I knew the higher pH lowered the acid usage but didn’t know that about the TA

Edit: sorry, had a brain fade with this comment, actually realised I suggested this in an actual thread I started a while ago

 

[JoyfulNoise]

I didn’t realise a lower TA contributed to a slower pH rise.
I knew the higher pH lowered the acid usage but didn’t know that about the TA

The offgassing of CO2 from the pool water is the single largest contributor to pH rise. TA in pool water is mostly carbonate alkalinity. As the pool water loses CO2, bicarbonate ions get converted into CO2 and that reaction consumes a hydrogen ion which results in pH rise. When the TA is lower, the overall amount of carbonate dissolved in water is lower and the slower the pH will rise.

Your pool water is over-carbonated relative to atmospheric levels of CO2 and so there is a constant driving force for CO2 to offgas from pool water.

 

[xDom]

The offgassing of CO2 from the pool water is the single largest contributor to pH rise. TA in pool water is mostly carbonate alkalinity. As the pool water loses CO2, bicarbonate ions get converted into CO2 and that reaction consumes a hydrogen ion which results in pH rise. When the TA is lower, the overall amount of carbonate dissolved in water is lower and the slower the pH will rise.

Your pool water is over-carbonated relative to atmospheric levels of CO2 and so there is a constant driving force for CO2 to offgas from pool water.

Ah yes, this actually ties in with the other questions I was asking on the other part of the forum

 

[Newdude]

I didn’t realise a lower TA contributed to a slower pH rise.

The 2 are joined at the hip, so to speak.

With a TA on the higher side it will pull the PH up.

With a TA on the low side of 'in range' it will help keep the PH down.

PH TA Relationship - Further Reading

www.troublefreepool.com

 

[Graham-11700]

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.

Home - AU
Home - AU

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

Hello & thanks for your research. I too am thinking about using Hydrochloric acid instead of Sulfuric acid with all the same questions.
I found this site which makes tubing for peristaltic pumps which shows which tubes perform better with specific chemicals including acids.

Chemical resistance chart for Tygon hoses I - Tubes International

The specifications apply to resistance at +20°C.

www.tubes-international.com

I'm guessing that the source of the fumes is the acid reservoir and so it should be possible to construct a DIY "fume cupboard" with an extractor fan to vent outside of pool house.
I read some comments about how much stronger/dangerous Hydrochloric acid is compared to Sulfuric acid, some alarming comments about fumes but I believe that excessive fuming occurs mostly when the acid is very strong (memories of the fume cupboard in school chemistry lessons). If the acid is diluted then this would REDUCE (NOT eliminate) the fuming and also the damage to the tubing.
If you have any new information then I would be please to hear it.
Thanks again
Graham

 

[Bperry]

I read some comments about how much stronger/dangerous Hydrochloric acid is compared to Sulfuric acid,

Where did you read that?

 

[JoyfulNoise]

I read some comments about how much stronger/dangerous Hydrochloric acid is compared to Sulfuric acid, some alarming comments about fumes but I believe that excessive fuming occurs mostly when the acid is very strong (memories of the fume cupboard in school chemistry lessons).

Any concentrated mineral acid can be “dangerous” when misused but sulfuric acid is far and away more dangerous from the perspective of handling and mixing it. Sulfuric acid can instantly cause skin burns and very deep tissue necrosis because the hydrogen sulfate anion (HSO4(-)) is very damaging to organic matter. Whereas in HCl, the counter anion is chloride (Cl-) which is innocuous to organic tissue. You can splash your skin with HCl and wash it off very easily, you can not wash off sulfuric acid fast enough before it will cause a chemical/thermal skin burn.

Hydrochloric acid can fume but the odor threshold of the vapors is much much lower than the concentration needed to cause any health concerns. So while HCl smells terrible (like a strong mix of vinegar and mustard), it’s mostly harmless. You should wear protective gloves and splash resistant eyewear when handling ANY pool chemicals but I’d much rather deal with HCl than sulfuric acid any day.

 

[arberito]

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.

Home - AU
Home - AU

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

Hi there!
I have been pondering over the same question as you have. New pool owner here, and have also just recently installed the MaxiUp dosing pumps from AstralPool. Rx Pump Programming And Calibration; Rx Proportional Dosing - Astralpool MAXI UP Programming Instructions Manual [Page 36]

I know for a fact that muriatic acid will work wonders on the pool if applied manually, but I am not totally sure if this type of dosing pump can process safely and without any damage a HCL of 15-20% concentration.

Have you figured out a way yet? By the way, isn't it ironic that astral pool sell their own hydrochloric acid of 32%, and yet caution against the usage of any other chemical but H2SO4? Hydrochloric Acid | Pool Acid | AstralPool Australia

Best,
Arbër