Drilling and tapping PVC to add injection point

squib

Active member
Apr 2, 2015
41
TX
My Stenner pump came in yesterday and now I am ready to install. I plan to tap into my return line somewhere downstream of my heater. My question is: should I tap into the PVC pipe or should I tap into a PVC fitting (90 or elbow)? The PVC fittings are thicker than just the pipe and therefore should allow my plastic for me to cut threads and make a more stable injection point. But I may be overlooking something. Any advice? I don't want to mess this up.
 
In my 50 years of experiences in the machine shop, tapping a tapered thread into the side of a pipe is a recipe for aggravation and leaks.....

What you want is an ? X ? X 1/2 reducing tee, where the "?" is a slip (glued) fit appropriate to the size of your existing plumbing and the 1/2 is a female tapered pipe thread. From that starting point, anything else should be possible.....
 
My pool is plumbed with schedule 40 PVC pipe so I just drilled and tapped a hole for the injection fitting right in the side of the pipe after the filter ( I don't have a heater). That pipe is plenty thick to handle the tapped fitting.

I've also read about people drilling and tapping a fitting for the reason you noted (it's thicker), but to me it's not a concern.
 
There is no slack in my plumbing to install a slip T. I would have to install two unions on the ends of the T and that seems like a recipe of added air leaks. I guess I can always just try to tap the pipe and if it causes problems, I can cut out that portion and then install the T. Thanks for the help.
 
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Went and checked plumbing. Saw this screw out port on the downstream side of my heater. Could I put a bushing in here and use it as the injection port? Am I looking at it wrong?
 
No, that is way too close to the heater/exchanger for injecting any chemical. I would not do that.

Even if I had no choice to put it on a heater run leg, I would want a check between the injection point and the heater. With the check being upstream of the injection point.
 

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Yes, downstream of the heater on the outlet. If you did decide to slip in a tee with unions, you have no worry about an air leak, since it's on the discharge side. If it were mine, I would insist on a check between the heater and injection point.
 
Yes, downstream of the heater on the outlet. If you did decide to slip in a tee with unions, you have no worry about an air leak, since it's on the discharge side. If it were mine, I would insist on a check between the heater and injection point.

Alright, just what I needed--a plan of action. I will move down the heater discharge line about 12 inches and install a check valve. Then downstream of the check valve, I will install a T between two unions with female threads looking up as a place to inject my chlorine. Seems straightforward enough. I will upload a pic when I am done. Thanks for all the help.
 
Alright, just what I needed--a plan of action. I will move down the heater discharge line about 12 inches and install a check valve. Then downstream of the check valve, I will install a T between two unions with female threads looking up as a place to inject my chlorine. Seems straightforward enough. I will upload a pic when I am done. Thanks for all the help.

At 12" from the heater, a check valve is not needed. You won't be injecting with the pump off. My injection point is in a tee about 30" from the heater outlet.
 
Got it all put in last evening in about 30 minutes. Decided against the check valve after I cut into the PVC and found that it had no water in it when the pump wasn't running. The angle of the pipe, I assume, means the water drains into the pool when the pump stops. As such, there appears to be no way water could back up into the heater.

Ran the pump on 5 for two hours this morning, and my FC jumped from 3.5 to 6. I have now turned it down to 2.5 and will try running it for about 2 hours a days and see where this maintains my FC.

Here are the pics for those that asked.
image.jpg

image.jpg
 
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