Plumbing Pside-Kick into PVC System

[FoxRedLab]

I just purchased a Pside-Kick to use with a pump in my drinking water storage tank. I intend to use 1-1/4" Schedule 40 PVC. Because the CSV1A has 1-1/4" male pipe threads on both ends of it, it seems that I will need to use a coupling on each end. However, it is not recommended to use a female-threaded PVC coupling on metal pipe threads because of the superior strength of the metal and the thermal expansion differential between the two materials. That does seem to be how it was done on the YouTube video, though, so I'm puzzled. Would I be better off using stainless steel female to female couplings (~$10 each!), and then installing a PVC adaptor with male threads on one end and a socket connection on the other? (It seems to be OK to install PVC male threads into metal female threads.)

Also, the clamps in the wall-mounting system for the CSV1A are sized to fit 1-1/4" pipe. Therefore, they can't be clamped around a coupling, and they won't fit between the coupling and the valve body. It seems, then, that they would have to be installed so that they clamp around pipe that comes out of whatever adaptor I use. As far as I can tell in the YouTube video, the clamps fit around the white pieces attached to both ends of the valve. I assume that the latter are PVC couplings that are female-threaded on the valve side with a glue-up socket on the other side. The outside diameter of such fittings is too large for the clamps I have to fit around them!

Am I the first person to have encountered this issue? I scanned the FAQs and could not find a similar issue.

[Cary Austin]

It shouldn't be a problem using female adapter to attach to the CSV.  There shouldn't be any thermal expansion on the cold water lines as this water stays the same temperature all the time.  However, you could use the SS couplings as you described.  Or you could use a 1 1/4" female slip X 1" male thread adapter if you had rather.  Or even switch to 1" a little ways before you get to the CSV.  A short piece of 1" is not going to cause much friction loss at 25 GPM or less.

The UTube video shows the Pside-Kick installed with 1" pipe.  So the wall mount fits around the 1 1/4" male threads on both ends of the CSV1A.  But if you use 1 1/4" pipe, just move the clamps down a few inches from the CSV and put the clamps on some of the 1 1/4" pipe.

[FoxRedLab]

Thanks! I hadn't thought about using an adaptor with 1" male threads and a 1-1/4" slip. That approach might be the best for the money, and I can see that the friction loss would be minimal.

A more general question: when installing threaded PVC fittings into/onto threaded steel, should any type of Teflon tape, pipe dope, or sealer be used? I know the answer for metal-to-metal and PVC-to-PVC, but can't find definitive advice for PVC-to-metal.

[Cary Austin]

Yeah you need a little Teflon tape and we use a little dope on top of that.  Just make sure you don't get the Teflon too thick or it will split the female plastic fitting.