$100 "Poor Man's" Acid Injection / Acid Pump

[matthewsunshineflorida]

120v BRS 2 Part Doser - $70
Stenner 1/4" Injector - $15
5 Gallon Jug - $15



It's a 120v pump, so I hooked it straight into an intellicenter relay for easy automation. Already had a cheap outdoor box for the plug to easily swap it out if it dies... Also had some old 1/2" CPVC and a rubber washer that fit perfectly - I just cut slits in the bottom of the CPVC to allow acid through and then pushed the tubing all the way to the bottom so the CPVC is a guide not an actual feeder tube. To vent it, I drilled some holes under the vent cap and then holes in the side of the vent cap itself, then put a few dots of hot glue to prevent tightening it all the way shut.

It doses SUPER slow (~3.5oz/hr), so I'm not overly concerned about tanking the ph but would like to have some more safeguards in place.

Not super exciting, but it took me a while to figure out the best way to do this so hopefully it's helpful to someone - or please feel free to tell me if I'm about to destroy my pool for some reason I'm not seeing lol

 

[JoyfulNoise]

I suggest you move that acid tank far away from the equipment. You do not want Muriatic acid anywhere near your gas line or gas heater. MA vapors are heavier than air and will “pool” around the area in stagnant air conditions. The vapors will rot away your heater in short order and could easily damage the natural gas line there. Not to mention the heaters exhaust is right there too.

 

[ajw22]

I would not inject acid before the SWG and have lower pH water flowing through the SWG. It can prematurely remove the rare earths that make the SWG work.

You can also get low pH water backflowing into your heater.

 

[rstrouse]

You know there is a Chem Doser component (different from the more advanced REM Chem) in njsPC that will maintain a max 24 hour dose volume and ensure the pool circuit is engaged while dosing. It will also maintain a dosing schedule based upon run-times.

 

[matthewsunshineflorida]

I suggest you move that acid tank far away from the equipment. You do not want Muriatic acid anywhere near your gas line or gas heater. MA vapors are heavier than air and will “pool” around the area in stagnant air conditions. The vapors will rot away your heater in short order and could easily damage the natural gas line there. Not to mention the heaters exhaust is right there too.

Good point and thank you for the heads up - what if I just connect a tube exhaust up above the shed or even off the other side of it, since the rest of the tank is sealed? I feel like I've seen pentair have something similar in people's photos.

I would not inject acid before the SWG and have lower pH water flowing through the SWG. It can prematurely remove the rare earths that make the SWG work.

You can also get low pH water backflowing into your heater.

On the off chance that the check valve fails, I was thinking the peristaltic pump should still hold the acid like a straw unless the pump is strong enough to overcome the vacuum, in which case the pump would be at least 20gpm which is a 1:4000 dilution ratio anyway, right? I would have the pump running both before and after the acid feeder stops, so any small residual would have hours to be pushed through. Where are you seeing the concern for this one?

EDIT: The pentair intelliph instruction manual says to install it between the heater and the SWG. They also don't mention a check valve, which you would expect them to know you wouldn't have since their SWG instructions don't recommend it either.

 

[matthewsunshineflorida]

You know there is a Chem Doser component (different from the more advanced REM Chem) in njsPC that will maintain a max 24 hour dose volume and ensure the pool circuit is engaged while dosing. It will also maintain a dosing schedule based upon run-times.

That's fantastic!! I'm going to have to look into how to set that up. I'm sure there's already documentation for me to find but feel free to point me in the right direction if it's a little buried.

 

[Flying Tivo]

Yes the Pentair intelliph has an exhaust tubing(breathing). Make sure you route that to the exterior. That is how i have it set up.

 

[matthewsunshineflorida]

Yes the Pentair intelliph has an exhaust tubing(breathing). Make sure you route that to the exterior. That is how i have it set up.

Cool, so I think I'm going to route an exhaust tube using the same method - rubber washer glued onto a hole that pretty tightly seals the tubing.

To measure the ph inside the plumbing, I just held a 1/4" tube up to a return at 20gpm for a few minutes to make sure I had a large sample size since the peristaltic pump turns continuously but releases acid intermittently, and the ph only goes down 0.2 at 20gpm (the lowest I run the pool). I'm wondering if Pentair suggests this before the SWG is because the aeration from the bubbles actually tends to result in a higher ph within the cell such that this probably only even balances it out to reduce scaling?

Last thing - I looked at the expected dosing rates on the intelliph and it almost exactly matches the pump I have, so I really don't see much about this system that would practically be any different.

 

[JoyfulNoise]

EDIT: The pentair intelliph instruction manual says to install it between the heater and the SWG. They also don't mention a check valve, which you would expect them to know you wouldn't have since their SWG instructions don't recommend it either.

The IntelliPH is also interlocked so that the acid dosed never runs while the SWG is producing chlorine. This is to protect the plates from generating in a very low pH environment where the ruthenium coating would become more soluble in water. For home brew setups like yours, it’s safer to inject at the last point of the return line to the pool.

 

[Flying Tivo]

I looked at the expected dosing rates on the intelliph and it almost exactly matches the pump I have,

I would not trust the specs too much. If you are going to run the pump with the intellicenter, then do a test run for 1 min pumping into a measuring cup. You will get exact real life results. My ET only runs schedules of minimum of 1 min. So i had to dilute the MA more and its easier on the equipment. I wired my ET to only be able to dose MA while pump is running(pump relay). For safety purposes.

 

[rstrouse]

At 1mL/minute your SWG would almost never run if you disable the chlorinator during dosing. The tank/pump for IntelliChem puts out between 105 and 125 mL/min after calibration. The Chem Doser in njsPC can also be set up to disable the chlorinator when dosing but you probably cannot take advantage of that with such a slow pump. There is a built in calibration mechanism to verify your flow. The important thing is that it should never be running when the pool circuit isn't engaged. If it is then you will eventually have more acid in the pipe than water.

It will also maintain your tank level and let you know when it is time to add acid.

 

[matthewsunshineflorida]

I wired my ET to only be able to dose MA while pump is running(pump relay). For safety purposes.

The tank/pump for IntelliChem puts out between 105 and 125 mL/min after calibration.

This is to protect the plates from generating in a very low pH environment where the ruthenium coating would become more soluble in water.

Really appreciate all of the counsel as I'm embarrassed to admit I just didn't know any of this! The reason I got this particular pump is because at ~1.5ml/min, it would be only a little over the 100% setting listed in the intelliph's manual i.e. 60ml/hr which is around 2oz to this one's 3oz. However, I don't think I realized that what the intelliph does is only run intermittently while dispensing 105-125ml/min during which the SWG is turned off because of the extremely acidic water?

I don't have any room whatsoever to move it past my SWG or to move my SWG, so I guess this leaves me with 3 options and I'd love to know what you think:

1. Get a faster pump like this (50ml/min) or this (up to 300ml/min), and use Chem Doser to handle all of the automation between it and my SWG
2. Run what I have all at once early in the morning with the pump on but the SWG off, adjusting dosing by extending run time earlier as needed
3. Let Chem Doser run it WITH the SWG since it's dosing around 1% of what Pentair's does, measuring a ph change of roughly 0.2 at 20gpm - if that wouldn't damage the SWG's ruthenium?

 

[rstrouse]

My recommendation would be to buy the Pentair Pump/Tank combo

522472​

and integrate it into njsPC Chem Doser. The tank/pump is done really well and you have adjustment of the dosing schedule at your fingertips. It also keeps track of every drop it dosed.

 

[matthewsunshineflorida]

Couple small updates:

1. Vent tube out and up high off a resin shed where some pretty good breeze tends to come by. This seem ok?
2. Tied the acid pump relay power to the load side of the pool relay and split off the SWG similarly, to schedule the SWG with no power when the acid pump is running.
3. Added a cheap countdown timer (B09BZ8LQFB), so if the pool and acid relays fail, this will cut power after the allotted max time. Currently have this on 4 hours which is around 15oz.
4. Since I already had a solar controller running in python, I added a few lines that check if the acid relay is running and make sure the reported GPM is 15+.
5. O-ring lube on the rubber washer and gorilla hot glue to help keep the vent tube and inlet in place.

I haven't yet spent the time on Chem Doser, but that's the ultimate goal for protection and convenience of having it dialed in, dosing more than just once, adjusting seasonally. For now, it's just running for about an hour and a half in the morning (~5oz) and I'm tweaking the time to find the sweet spot like an SWG.

I didn't know I could get a Pentair tank/pump combo when I started this, but I just don't want to spend more money when I have something working. I also kind of like the idea that it's feeding acid SO slowly (3.5oz/hr) that it seems less likely to cause problems, especially being behind the SWG and SO close to the heater. Speaking of which, the heater is not working so that's the next thing I have to figure out. Time to read some threads and bring out the multimeter...

 

[matthewsunshineflorida]

This has worked great so next, I'm trying to experiment with Chem Doser. However, I'm wondering if I should just let it dose throughout the day and not worry about the SWG if it's truly a 0.3ph drop max?

• I measured 0.2ph drop at the returns at 22gpm, but I think the math also confirms this:
  • I figure 1.8 ml/min (with no backpressure so probably less with the pool pump on).
  • If the pump is at the lowest pool speed at 22gpm that's 1.8 ml/84k ml.
  • This is equivalent to 36oz in my 13k gallon pool i.e. Pool Math says no more than a 0.3ph drop. It's set to run at twice that speed so 0.15ph drop max inside the cell would be typical?
• Right now, I have the SWG and acid pumps on two separate relays with their line side being fed by the load side of the pool, so neither can turn on without the pool and but they can run separately.
  • The pool + acid run from 7:30-9:30am and the SWG relay turns on from then until 3am (no power when pool shuts off but turns on if spa comes on at night).
• With the manual countdown timer set at 4 hours, it physically cannot release more than 15oz over a long period in a worst case scenario that all relays fail and the pump just runs.
  • Compare this to the intelliph which can apparently dump 100-125ml/min i.e. 2 gallons per HOUR?
    • Only advantage with intelliph seems to be the flow switch - guess I could put one in unless someone knows how to tap the SWG's?

I'm not seeing the value add in getting the intelliph tank/pump, and I'm kinda wondering if this may even be a safer alternative that can actually just run WITH the SWG - am I crazy?