Homemade Acid OR Chlorine Injection System

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
Re: Homemade Acid or Chlorine Injection System

Shwim, did you use full strength bleach in the tank?

Another option although not quite as attractive is to use more tanks or a larger tank and dilute the chlorine. This has two advantages. One is the chlorine is less subject to degradation and two, the formation of crystals may be somewhat reduced. You wouldn't need as many drip buttons either since flow rate would need to be higher for the diluted solution. However, I'm not sure how much dilution would be needed to eliminate the cyrstals.
 

schwim

Member
Sep 3, 2007
21
Re: Homemade Acid or Chlorine Injection System

mas985 said:
Shwim, did you use full strength bleach in the tank?
Yes. I don't see diluting as an option. My pool is "far" from the house. It's hard enough lugging the jugs of chlorine out to the filter every week.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
Re: Homemade Acid or Chlorine Injection System

If you have a water source at the pad, pool or fill, you could dilute the chlorine at the pad. This requires that you have a water source at the pad but most builders put in a siggot in the pool plumbing somewhere. A long hose works as well.

If you take 4 water jugs like the one in the picture and connect them with 2-way drip splitters so they combine into one line and then connect that line into the drip buttons, this would make it easiler to dilute the chlorine. One jug could contain the chlorine and the other 3 could contain just water. Or you could put 1+ gallons of chlorine in each jug and fill the rest with water. Either way this will dilute the chlorine running through the buttons. This might be enough to prevent the cyrstals from forming.
 

lnorris

Active member
Dec 28, 2008
31
Houston, TX
Re: Homemade Acid or Chlorine Injection System

Can you describe in more detail what is required and the procedure to tap into the return PVC pipe. I defintely don't want to make a mistake that would cause a leak or require a patch.
 

schwim

Member
Sep 3, 2007
21
Re: Homemade Acid or Chlorine Injection System

lnorris said:
Can you describe in more detail what is required and the procedure to tap into the return PVC pipe. I defintely don't want to make a mistake that would cause a leak or require a patch.
I didn't tap into the return, although I suspect others have. I connected to the suction-side drain of the pump housing. The pictures above should show how I did it. Your pump may be different and not have that drain.
 

Aquaman95

Well-known member
Feb 20, 2008
249
Re: Homemade Acid or Chlorine Injection System

Tapping is pretty simple. Just go slow and easy. Most injection fittings will be threaded 1/4 male NPT. That means you need a 1/4 NPT tap. The correct drill bit size to make the hole before you tap (thread) it is 7/16". Yes, 1/4 NPT is not 1/4"; it is larger.

You can get the correct drill bit and tap at Home Depot. When buying the drill bit, make sure you buy one that has a "turned down" shaft (shaft is smaller diameter than the bit itself). This is because the most common home drills only accept up to a 3/8" shaft.

When selecting a location to tap in your system, I recommend an elbow simply because there's more thickness there.

Drill the 7/16" hole straight into the pipe (one side only)!

Deburr it.

Thread the tap down in the hole slowly. You may need to back it in and out a few times to keep the threads clean. Just thread the tap back in and out of the same threads.

Only insert the tap a total of 1/2" depth. That's all you need for most fittings and if you go too deep with it there won't be enough depth in the threads on the fitting to get a good seal. You cam mark the tap with some tape before you start and just stop when you get to the right depth.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
Re: Homemade Acid or Chlorine Injection System

First choice would be to use the pump drain plug but if you have a spa, it might be a good idea to introduce the acid up stream on the pool suction only so acid is added only in pool mode. I found that the SPA PH would drop fairly low with a couple of hours of use.

What I did was to use a drip irrigation barb (barb on both ends) and cut off one of the barbs. I drilled a small hole into the pool suction side plumbing and then hot glued it in with the barb sticking outward. Then used a 1/4" drip hose from the barb to the tank. Because of the suction, this seals fairly well and doesn't require a large hole in the pipe. Also, the hot glue not only seals well but is easy to remove and plug if necessary.
 

lborne

Well-known member
Jun 29, 2009
467
Vero Beach, FL
Re: Homemade Acid or Chlorine Injection System

I really like this idea, but don't want to introduce acid before my SWG. Please tell me your thoughts on this idea:

Insert a T fitting after the pump with a ball valve to divert a portion of the flow to a 3/4" hard pvc (or flex) line. In line of this 3/4" parallel branch line I would add a venturi tee http://www.lagunakoi.com/subcat159.html and a check valve. Then the line would reconnect to another T downstream of the SWG on the return line. Then all I'd need to do is connect the acid feeder line from the storage tank to the input on the venturi tee.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
Re: Homemade Acid or Chlorine Injection System

I had considered using a Venturi tee but the output port has to have less than a few PSI of pressure or the water will start to backup out the air port. It might work if you could get it close enough to the pool or with it's own very large return pipe. Connecting it back up stream may not be low enough pressure but you could give it a try.

I have a SWG and have been using this setup for a couple of years now without any problems. In fact, I believe that it helps somewhat to keep the SWG clean (less PH bounce). One thing to keep in mind is that the amount of acid introduced is very small so the PH of the water going through the SWG is only slightly lower than the PH of the pool water but well above the minimum requirements. Generally, it is only about 0.1-0.2 PH difference and not much different than if you added the acid all at once to the pool. This is the reason I went ahead with the setup because I was very confident that there would be very little risk to the equipment.
 

lborne

Well-known member
Jun 29, 2009
467
Vero Beach, FL
Re: Homemade Acid or Chlorine Injection System

mas985 said:
Generally, it is only about 0.1-0.2 PH difference and not much different than if you added the acid all at once to the pool. This is the reason I went ahead with the setup because I was very confident that there would be very little risk to the equipment.
Thanks. I just ran the numbers based on an estimated usage of 64 oz acid per week (pool is not finished yet), and the gpm of the pump, run time, etc. and came to worst case of .23 ph difference. I like your solution much better as it is so simple.
 

lborne

Well-known member
Jun 29, 2009
467
Vero Beach, FL
I've bought all the parts but just thought of another potential problem. I'm worried my wife, or myself :), might forget to turn off the acid when we switch to spa mode. The setup is using a single pump. In this case, I'm now thinking of going back to the venturi in the return line to the pool only.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
I take it you are introducing the acid at the pump drain plug? As I outlined a few posts above, you could drill a small hole in the pool suction pipe and introduce it there. This is the way I now have it set up in my system and it works pretty well. I use hot glue to hold in the barb.

Otherwise, it may take a while to lower the PH of the spa and if you use the jets a lot, it may help to keep the PH up. So you might want to try it once and measure the PH of the spa to see if it actually gets too low. It may not.

When I had the line in the drain plug, it took about an hour before the spa PH dropped to 7.2 from about 7.5. So even then it wasn't too bad but sometimes the kids use it for hours so I wanted to make sure there would never be an issue.
 

msm859

New member
Sep 26, 2009
2
Ok I tried this setup. I have an Intelliflo VS pump and I started with a couple 1/2 gph buttons and kept adding to reduce the draw until it actually stopped (only about 6). Then I reduced them and the draw is very sporadic from day to day. what's up????
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
Do the pump speeds differ between the days? Varying pump speeds changes the suction at the pump so you will get different draw rates for different speeds. If the speed is kept constant or follows a schedule each day, then draw rate over the course of the day should be the same.
 

msm859

New member
Sep 26, 2009
2
No, the speed is the same throughout the day -- runs about 12 hours. I did use pressure compensating buttons if that makes a difference.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
It might make a difference. I have never tried those so I don't know what they would do.

Also, what exactly do you mean by sporadic? How much does the flow rate change from day to day and how are you measuring it?

Things that can change the draw rate (i.e. pump suction)

Solar
Suction or pressure side cleaner
Valve changes
Pump speed

But if all the above are exactly the same day to day, then the draw rate should be abount the same. I get variations mainly due to solar since it is automatically controlled.

The day to day variations are not all that important. What matters is the average draw rate over a period of days or a week. If one day is a bit more than another, it shouldn't matter much.
 

lborne

Well-known member
Jun 29, 2009
467
Vero Beach, FL
Below are some photos of my setup. I finally installed it last night. I have a new plaster pool which is taking lots of acid. The parts were laying around the garage, so I worked with what I had. I drilled and tapped 7/16-20 into the 90 elbow for the pool drain feed and threaded a stainless fitting with o-ring seal. I'm using 4 half gallon drip buttons for now. Problem with the drip buttons is that they seam to leak a bit of air and overnight the pump lost its prime. It only takes a minute to get back, but I still want to avoid that. I will hot glue the connections like Mark S has done.

I'll spend the next couple weeks getting the feed rate just right. I'm diluting at a ratio of 2:1 but may raise this to 3:1 if the feed rate is faster than I expect.[attachment=2:32wn6neh]P9293082 (Medium).JPG[/attachment:32wn6neh][attachment=1:32wn6neh]P9293083 (Medium).JPG[/attachment:32wn6neh][attachment=0:32wn6neh]P9293085 (Medium).JPG[/attachment:32wn6neh]
 

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mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
Nice setup. I especially like the green hose. Adds color.

What I found works well for the buttons is to hot glue the barbed end and use plumbers grease on the smooth end. This seems to seal fairly well while allowing for removal or addition of buttons.

Let us know how it works out.
 

lborne

Well-known member
Jun 29, 2009
467
Vero Beach, FL
Well, I'm still trying to find a leak. I eliminated the valve and drippers and just had the hose go from the container (which I completely filled with acid and water) and let it sit overnight. It let air into the inlet which made the pump basket fill with air and then it siphoned about 25% of my mixture.

I am certain that the system was sealed before I added the fitting and hose. I'm also certain it is not the fitting on the 90 elbow as I've used those before and they are pretty good about sealing - although I'm trying another one just in case. I'm thinking the tank might still siphon until water levels are the same, even if there is no air leak in the line.

Any suggestions? I'm just going to give it a try once more using a jug of water overnight to see if I can stop the siphon.