NPS connection to NPT

Was hoping someone might be able to help me with a piping issue on a mag drive 9.5. Currently I have my mag drive pump connected to a pvc pipe return from my sump. At the time I made this connection the pvc cracked the threaded connection on the pump when I was tightening down the fitting. I made due but now understand why. It appears the connection on the pump is a NTP( National Pipe Thread) not a NPS (nominal pipe size). From what I can find NPT has a tapered thread thus the reason for the crack when tightened down.

I would assume there is some adapter to change NPT to NPS. Anyone have some tips or tricks to connect a NPT fitting to NPS for PVC?

 

Threaded PVC couplings and fittings are NPT or taper threads. The Mag pumps also use NPT or standard tapered pipe threads.
Things like garden hoses and hose fittings are not NPT in that they have no taper, they depend on a gasket, o- ring or washer to seal while tapered threads seal on their own due to the taper, the further you ecrew it on the better it seals.

If your threads did not match it is because the PVC was not NPT and may have been a hose thread. Lowes and HD sell both so it could have been in the wrong box or bin.

Always use a few wraps of teflon tape, do not use too much which will cause a crack, or better yet the crayon type thread sealant like LaCo Plasto Joint which can be found at any hardware store.
LA-CO: Product Detail - PLASTO-JOINT STIK® - Plastic Thread Sealant

My swimming pool was plumbed with PVC in 1983 and all the joints used Plasto Joint and do not drip or leak to this day and the stuff is still pliable which is amazing in Phoenix heat.

 

Thanks for the reply, figured someone would know. I'll give the Plasto a shot when the replacement part come in for the mag drive.

 

Before you assemble the treaded connections take a minute or two with a nail file, jewelers file or pocket knife and clean all the excess flashing or plastic molding out of both the male and female threads. You would be amazed how much better things screw together and stay water tight when the threads are clean. It also keeps the teflon tape from shredding or tearing or the putty stick from scooping out of the threads. This is especially on bulkheads, I have written several stickies on various forums on how to properly install bulkheads, including this one I believe.

What part of town are you in by the way? Do you attend any of the local meetings or trades?

 

I'm over on the East side of town in Chandler. We usually go to Aquarium arts for most of our simple fish supplies because it is the closest store. What about your self, area of town?

As for the meets, haven't ever been to one, though I would be interested if you know of some good ones. I have a ton of Kenya tree corals that I would love to give away, though not too many people want them since they grow like weeds which I can attest to.

 

There is a local forum www.azreefs.com where you can find details on FRAG and PROP meetings as well as occasional AZ Reefs group meetings.
I am in the Deer Valley and was a 3 time President of the now defunct Desert Marine Society which had been around for 20 years or so before the internet, frag trades and group buys kind of killed formal clubs which depended on local fish stores for donations and prizes.