Acid Injection

[jerryk1234]

To maximize the life of my newly installed Hayward H400FDN heater, I have decided to get the PH under control. Yeah, I know you can just dump acid in the pool, but I
get forgetful...

I bought a Hanna BL100 acid injection system. This has a controller, a peristaltic pump, and a PH sensor. Now, I'm not really sure this will be less work than just dumping
the acid - PH sensors always require babysitting in my experience - but I'm willing to give it a try. Still have to keep testing the water, you can't just leave it on faith.

The Hanna doesn't come with any acid reservoir. So I bought a Pentair acid tub. It's $$$$, but it's made for this application. Has a base that you can screw into the concrete, and some sort of bottle-seal piercer so you can just upend the new jugs of acid into it.

The Hanna also came with a remote see-through cannister for the PH sensor. Two hoses go from the cannister to the pool plumbing, and each one has a turnoff valve. This should allow
me to service the PH sensor without draining the whole equipment pad. I have identified where the PH sensor can go, and also where the acid will be injected - last thing before the water goes back to the pool.

The most complicated thing here is the control for the Hanna. It must NOT inject when the pump is not running. How to figure that out? The E-Command-4 doesn't have any specific output for that. The main pump power is not switched; the E-command-4 talks to the pump via some sort of multi-wire low-voltage protocol. The most straightforward thing would be to tap into the salt system's flow switch. This produces a switch closure when water is flowing.

I don't know if I can just connect the Hanna in parallel with the salt controller ( Hayward Aqua Rite ). The Hanna has a "digital input". No info available beyond that.
Don't know if it's 5V logic or 3.3V or....?

I don't know if the Hayward input is referenced to ground, or floating. I'll figure it out by making a little breakout card to go between the Hayward and the flow switch. Then I can stick a meter on it. The input to the Hayward is a 6p4c ( six places, four contacts ) modular phone connector. There are only two wires in the middle of the connector. I just got a baggie of those connectors from Amazon, and I already have the crimping tool.

I read about the Hanna on this forum...

 

[PoolStored]

maximize the life of my newly installed Hayward H400FDN heater

Low pH is the big cause of corrosion. Elemental copper develops a patina of copper oxide, which protects the copper from further oxidation. Low pH is what strips off the copper oxide and exposes the elemental copper to oxidation from chlorine and oxygen. I would not set your pH to go to 7.2 constantly. 7.6 is a good target.

The most complicated thing here is the control for the Hanna.

Read all of section 1.4 here. I would vote current sensing relay.

SWG How It Works - Further Reading

www.troublefreepool.com

 

[jerryk1234]

7.6 would be fine.

 

[Bperry]

To maximize the life of my newly installed Hayward H400FDN heater, I have decided to get the PH under control. Yeah, I know you can just dump acid in the pool, but I
get forgetful...

I bought a Hanna BL100 acid injection system. This has a controller, a peristaltic pump, and a PH sensor. Now, I'm not really sure this will be less work than just dumping
the acid - PH sensors always require babysitting in my experience - but I'm willing to give it a try. Still have to keep testing the water, you can't just leave it on faith.

The Hanna doesn't come with any acid reservoir. So I bought a Pentair acid tub. It's $$$$, but it's made for this application. Has a base that you can screw into the concrete, and some sort of bottle-seal piercer so you can just upend the new jugs of acid into it.

The Hanna also came with a remote see-through cannister for the PH sensor. Two hoses go from the cannister to the pool plumbing, and each one has a turnoff valve. This should allow
me to service the PH sensor without draining the whole equipment pad. I have identified where the PH sensor can go, and also where the acid will be injected - last thing before the water goes back to the pool.

The most complicated thing here is the control for the Hanna. It must NOT inject when the pump is not running. How to figure that out? The E-Command-4 doesn't have any specific output for that. The main pump power is not switched; the E-command-4 talks to the pump via some sort of multi-wire low-voltage protocol. The most straightforward thing would be to tap into the salt system's flow switch. This produces a switch closure when water is flowing.

I don't know if I can just connect the Hanna in parallel with the salt controller ( Hayward Aqua Rite ). The Hanna has a "digital input". No info available beyond that.
Don't know if it's 5V logic or 3.3V or....?

I don't know if the Hayward input is referenced to ground, or floating. I'll figure it out by making a little breakout card to go between the Hayward and the flow switch. Then I can stick a meter on it. The input to the Hayward is a 6p4c ( six places, four contacts ) modular phone connector. There are only two wires in the middle of the connector. I just got a baggie of those connectors from Amazon, and I already have the crimping tool.

I read about the Hanna on this forum...

Just a mention in case it wasn’t known already…If you let your TA settle down at 50-60ppm, your Ph will be pretty stable and you may not need anything installed.

 

[ajw22]

Just a mention in case it wasn’t known already…If you let your TA settle down at 50-60ppm, your Ph will be pretty stable and you may not need anything installed.

Discussion with Jerry about pH is here…

Hayward H400FDN temperature sensor

Inadequate gas supply. Piping too small. This last is what he thinks is the problem. Back at the house, there's a small-diameter pipe connecting the "house" stuff to the pool stuff. Also - the earthquake valve is too small. If that's true, I have a bone to pick with my pool builder. If their...

www.troublefreepool.com

 

[jerryk1234]

OK, thinking carefully about this "flow switch that can fail". If we inject acid without the pump running, bad things can surely happen. I feel a need for "belt & suspenders". I think I'll use both the flow switch AND a current sensing relay. Power the BL100 through the current sensing relay ( the folks at Hanna assured me that powering it down unexpectedly was OK ), and hook the switch to the "level switch" input, which is supposed to
condition output on a float switch in the acid tank. The Hanna people told me that the "alarm" functionality associated with that switch can be turned off. In this case "failsafe" definitely means "fail by not injecting".

 

[jerryk1234]

Just a mention in case it wasn’t known already…If you let your TA settle down at 50-60ppm, your Ph will be pretty stable and you may not need anything installed.

TA is 80. The pool constantly trends alkaline. It has always trended alkaline.

 

[PoolStored]

TA is 80. The pool constantly trends alkaline. It has always trended alkaline.

And it will.

High TA, low pH and aeration make pH rise faster.

You may find that with a TA of 60-80, your pH will be stable 7.8-8.0. Doesn't really matter, you have now bought the thing. Now that we know your TA is 80 or below, I would not drive your pH to 7.6 or lower, I'd target 7.6, when your TA is 80 or below. If you drive it lower, you are likely to drive TA below 50 over time. You need to monitor your TA with your injector. You want to keep pH and TA stable around 60-80.

If you have high TA fill water, you will be fighting this ongoing.

PH TA Relationship - Further Reading

www.troublefreepool.com

Managing pH and Total Alkalinity - Further Reading

www.troublefreepool.com

 

[jerryk1234]

Interesting. So what TA would make it tend to stay 7.6 to 7.8? I need to test our tap water and see what we're filling the pool with. There is a service based out of Sacramento that can come and reverse-osmisis filter the water, but it's very expensive - I was quoted $800 for a visit. $800 can buy a LOT of acid.
The pool does not get a lot of aeration. We have a power cover, and it is ALWAYS closed when we are not swimming or doing pool maintenance.

 

[PoolStored]

Every pool is different. With a TA=50-80, your pH would be stable between 7.6 and 8.0.

Why are you fixated on 7.6 to 78?

 

[jerryk1234]

Fixated on 7.6 to 7.8? Maybe because I'm on my third heater, and I'd like this one to last. So trying to dot all my I's and cross all my T's. I don't *know* that PH was the cause or even contributing. I do know that at 8.00 or so my eyes start to sting.

 

[PoolStored]

The typical eye pH tear content is 7.3 to 7.4. (https://jamanetwork.com/journals/jamaophthalmology/article-abstract/632077)

The comfort range is is typically 7.2 to 7.8. It is possible for irritation with PH >8.0, but is more likely with pH < 7.2, In addition heater corrosion typically happens with lower pH.

As for heater, and eyes, pH < 7.2 with be more acidic and cause more irritation on eyes and heater damage, than pH > 7.8.

Target TA at 60-80 and a pH of 7.8 to 8.0 and you should protect your heater and eyes...

 

[uraceulose]

I also use a BL-100 for acid injection. Wired it to a wifi timer that is powered to run off the same circuit as the Pump/SWCG. If the pump/SWCG don't have power, the wifi timer won't either so the injection pump won't run if that power ever goes out.

Also have a flow sensor and level sensor so if the flow stops, it would also stop the injector or if the level in the acid tank ever dropped low enough it would stop injecting as well.

The tank level sensor is really more of a monitor than a redundant shut off and really overkill...it would take 2-3 months to go through the acid and not really the end of the world for the peristatic pump to run dry if it did.