What return point for acid?

[bcatv]

Hoping to hook up my acid and chlorine injection pumps this weekend, and while the best return point for the chlorine seems obvious, (the floor cleaner heads, since that way the new chlorine will be swept over all the plaster surfaces first), I don't think I want to put acid over the plaster, not to mention the springs in the heads themselves. I really only have two other convenient (piping at the pad) choices: four floor returns that are distributed along the long axis of the bottom, or six bench jets that have omni eyeballs but generally shoot straight out into the end of the short leg of the L. (I suppose I could use the fountain line and have the acidifed water shoot through the air and land in the middle of the deep end, but somehow that just seems like a bad idea...) The floor returns seem like the best path, but the current fittings are omni cone/slots that may not keep the incoming acid far enough away from the plaster, I haven't felt the flow direction yet. What do you think, gurus?

Also, the nice-looking injection fitting that came with the pumps is .25 NPT, which will require me to drill a .44 inch hole, then tap it, and I'm just wondering about the width/depth of such a big hole in the PVC. I've got a 2.5 inch elbow available for the chlorine, but only 2 inch for the acid; any experience tapping that size hole in PVC?

 

[Aquaman95]

I would inject both in the return line that goes to the eyeball fittings. Both chemicals will be highly diluted by the time the reach the pool but no reason to take any chance with metal parts in the floor cleaning system.

No problem tapping 1/4 NPT into a 2 or 2.5" elbow. Elbows are actually the best place to tap because they are thicker.

A few tips:

If you have a 3/8" drill chuck be sure to buy the turned down shaft 7/16" drill bit you will use to drill the hole, otherwise it won't fit in your chuck.

When tapping, tap straight.

Don't tap too deep. 1/2" deep is plenty.

Be sure to electrically interlock the pumps with the main pool pump. You don't want them pumping when the circulation pump is off. You could also interrupt them with a pressure switch.

 

[bcatv]

Thanks Aquaman, good advice. On the chlorine inject, though, after reading Chem Geek's estimate of chlorine demand in the spa with a crowd, I think I will inject before my pool/spa valve so that I can use the pump to steadily add chlorine to the spa during spa-mode use; my previous idea of just having a couple of pucks in the spa skimmer seems way undersanitized compared to the 90oz of bleach that 6 people x 3 hours yields.

 

[JasonLion]

You only want chlorine injected before the pool/spa split if your system is clever enough to use a lower feed rate when in spa mode. Feeding chlorine into the spa at the same rate as you feed into the pool will put way too much chlorine into the spa.

 

[bcatv]

Well, the system won't be, in the beginning, but since the pumps have electronic variable interval timers, if I knew how much I wanted I think I could adjust the pump to deliver it. A little manual, but Chem Geeks numbers make me wonder if most spas don't run down to zero chlorine frequently. How would you meet the demand?