Mixing schedule 40 and schedule 80 okay?

[dragoneggs]

Alright... I have been splitting several schedule 40 1in valves during the set up of the plumbing for my new tank. I can't figure out why except to think now that the schedule 80 1in male/slip adapters are the culprit. I have been putting 5 turns of teflon tape on the threads and tightening them just beyond hand tight. There is still a couple of threads showing on the adapters. A couple of the valves split a day after install while the pump was running.

 

[Scooterman]

I went from sch. 80 bh's to sch. 40 threaded with no problems but on the pumps all was 40. I burried each fitting that was threaded using about 5 rounds of teflon. I wouldn't use sch. 80 on anything but the BH's, you don't need the overkill & it is probably the problem because the sizing of the threads seem to be slightly different.

 

[IAP Brian]

Hard to say. I have mixed sch 80 & 40 parts for 15 yrs without a problem. I have even thrown electrical conduit parts in the mix just to keep all the plumbing grey colored. Overtightening can be a huge problem but cheap crappy parts are even worse. You may have also gotten ahold of a bad batch of valves. Are they splitting down the mold seam of the valve?

 

[dragoneggs]

Hi Brian, Scooter,

Yes they are splitting on the parting seam on the threaded side. I am not bottoming out the thread and I am tightening just beyond hand tight. It is hard to believe that I am overtightening them but I may be...

I know it is overkill to go sched 80 but I wouldn't expect them to split the valve! These are Spears valves.

 

[jsmkmavity]

same threat just thicker wall plastic and more ridgid. you dont need sch 80 for anything in tank plumbing but unions and any female thread fittings are better in sch 80. i use glue joints and flexible pipe whenever possible and then a union and ball valve.

 

[dragoneggs]

Yeah I used flex and glue for almost everything except the valves.

 

[jsmkmavity]

sounds like a bad batch. all pipe fittings are tapered thread and designed to put pressure/stress on the opposite fitting. when tightened properly it should be one to three turns past hand tight and with teflon tape it shouldnt take much force to achieve that, and that should not split a fitting. if the fitting turned smoothly the whole time and diddnt stick or squeek then you have enough teflon.

 

[dragoneggs]

sounds like a bad batch. all pipe fittings are tapered thread and designed to put pressure/stress on the opposite fitting. when tightened properly it should be one to three turns past hand tight and with teflon tape it shouldnt take much force to achieve that, and that should not split a fitting. if the fitting turned smoothly the whole time and diddnt stick or squeek then you have enough teflon.

Definitely did not go past a turn after hand tight. 5 wraps of teflon and I recall it being kindo of sticky. Maybe I should refit these with more teflon and only hand tight and see if it seals. I have 10 valves on 5 pumps! 4 of them CL and 1 for the main sump/filter.

 

[Scooterman]

If they are breaking on the seam like Brian said then you have valve issues, I would contact the place you got them & see if you can replace them all.

 

[dragoneggs]

Already doing that and they are taking them back and replacing so no worries on cost... just a lot of hassle. I still can't believe these are breaking at such a high rate!

 

[tamarindthai]

i had sc 40 split under the tank /returen pump at the restaurant once,,woke me up 3am drove to ,,what i saw not pretty picture at all ,,go for sc 80 and still do not over tight,,good luck

 

[IAP Brian]

These are Spears valves.

wow that stinks. I would say they are a bad batch. I have seen poor quality parts split along their seam but I would not expect that from Spears. They charge waaaaaaaay too much for their plumbing parts to put up with crap. Glad to hear the store is swapping them out for new ones.

 

[fxdp]

You should not use teflon tape on the connection. This is a partial cause of the failure of your fittings. Nor should you use teflon dope on the connection (too slippery -- leads to overtightening). Only use a non-hardening sealant approved for plastic, then finger-tight the joint and go 2-3 more turns MAX. See: Assembling Threaded Plastic Fittings | LASCO Fittings for a full explanation of threaded plastic fittings and their use and limitations. It has an informative explanation of the splitting forces created in plastic fittings when joined with tapered pipe thread. It will explain why your connectors split.

 

[Vlad2spinn]

@fxdp, very good information. I was going to respond with the same information you did, but then realized this thread is from 2007