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Threading PVC

Posted by PupillaCharites FL 9a (My Page) on
Wed, Sep 11, 13 at 13:05

Really, threading PVC on the cheap. Anybody threaded a 1/2 or 3/4" schedule 40 PVC regular thick wall pipe with a female pipe thread made of iron and gotten results that can be done and undone many times successfully in a hydroponic, low pressure (2-3 psi) system?

I know there are dies for this and there is a good thread in the archives about that, but I don't want to buy an expensive tool, just a cheap female pipe thread fitting, maybe an elbow for turning torque, FNPT fitting, from the plumbing part bins at Lowes. And how about the reverse using say a nipple, or is the wall too thin to do any good?

This post was edited by PupillaCharites on Wed, Sep 11, 13 at 13:09


Follow-Up Postings:

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RE: Threading PVC

Not sure but I replied to follow the thread.


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RE: Threading PVC

That makes two of us wanting to know, help, y'all!

Both PVC & iron pipe have the same OD, thread and I think minor taper.


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RE: Threading PVC

Are you thinking of using this for a drain or spiget type setup?

I made drains by using a 1/2" male threaded fitting, a #15 o-ring (on both sides) and then a faucet flange fitting (I think that is what they're falled).. I've linked a picture as a side drain on mine for a nursery channel. You can use them on the bottom and get a really low drain by notching the flange nut and the male's threaded area.

That said.. if you want to join two pipes and not make a bulkhead fitting - I found using the same flange nut here on the threaded male fitting, then an oring, THEN the female fitting.. The taper on the thread makes it nearly impossible to get a watertight seal without cranking down so hard that you cant get it off easily. Teflon tape helped as well to make it smoother on and off.

Not sure if that helps - but might give you an idea to use something like an o-ring instead of relying on the thread taper to seal. The o-rings seal up with just a few inches of tourque on it.

Here is a link that might be useful: Flange picture


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RE: Threading PVC

I've made a tap by cutting vertical grooves in a brass nipple and it worked ok, but ended up spending the $15-20 to get the professional tap from ACE Hardware which worked much better. I have also used a die to put threads on the outside of a pipe (3/4" and1/2"). Your are not supposed to thread schedule 40 but I did anyway. It worked ok but was very difficult to get straight, but still worked. My advice...try the tap, stay away from the die. Use HDPE fittings or any non PVC plastic fitting to go in a threaded PVC hole. You will not need Teflon tape and will be much easier to remove.


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RE: Threading PVC

nek & SD,

thanks so much for your suggestions and experiences. I'm behind and flying by the seat of my pants so I don't know what I'll end up doing but both of your suggestions are very helpful and the starts arrive next week. Hopefully we'll be out of the 90's by then, kicking off my season, without every single day for a week being rainy like the forecast.

Great ideas with PE and nice go at craftsmanship in the link.


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RE: Threading PVC

I still need to work on doing better with the points mentioned in this thread. For the moment I'm just putting an elbow going down w/reducer at the end of an inclined drain trough to carry the drain back to the res. It's provisional but the plants can't wait, heck they are crying for planting; hope the 3" pvc with a sliced off top does ok as the drain collector from the channels so I can work on the rest in time. It's much smaller than I had planned on but it was free so I hope that's not a mistakle for a ttl 9 liter per minute flowrate coming off 4 and 5" channel bottoms.

I thought of just putting a large funnel to have it pour into a drain, but I was too scared of the possibility of disasterous misalignment outside the protection of the supports in that corner.


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RE: Threading PVC

I have 5-6l/min draining thru 3/4 with plenty to spare, so I think you should be set!


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RE: Threading PVC

Thanks nek. I just don't like the design of the sloping collection trough where the water falls in, getting further and further at the low end. After it starts working I'm gonna have to redo the way water exite the channels. Thought of putting it horizontal anyway but I have other worries on that. I only reduced it down to 2" from the 3" collection trough. The dang reducers cost more than the extra for the of pipe, I was thinking of going with 1 1/4" so even 3/4" works, huh. Oh well, my neighbors might gawk at the big hydroponic spaghetti monster, just hope the HOA is dead and buried ;-(


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RE: Threading PVC

You have a picture of the drains at the end? I think I can imagine it, but it does sound like a ton of plumbing (and expensive).

I might have posted these before... but gives you another option. I took a 4x4 pvc fence post cover and ripped 1" out of a corner. Then put a drain in the bottom of it. The only issue is I have to use a spreader type mat (read as: fleece from joanne fabric) at the end (somehow secured) so it'll drain straight down.. if not, it will creep back up the channel and wet the floor.

NFT end drain

Drain with spreader mat


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RE: Threading PVC

I know how the creeping water looks!


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RE: Threading PVC

Oh, honestly the plumbing isn't bad pricewise in the big scheme of things, but everything sure added up. My channels are also square, but I don't have one to spare for a drain and because they are free of recycled material and interior UV stabilizers and I already used up my good will with the extrusion guys that I can't pull a Colombo 'Just one more thing' on them. The plan had been to use a six inch pw pvc pipe, but then I got thrifty when I got the 3" pw piece free.

Ha! I'm glad the JoAnn's fleece worked out for you. My current finishing plan in that department if the water curls (still hasn't seen 'first flow') is to just fasten my fleece at the the channel end. This assumes I don't have to mat the whole thing because of leveling issues with our sandy ground where sink holes are thrown in at no extra charge.

I'll post a pic when it's working later this week. It is still incomplete and I have suffering strawberries needing their nutrient fix, fast!


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