Leaking membrane fittings.

[Tweegs]

First, a quick update on my homebrew RO.
Two XLE-4040’s in series, 240 GPH Procon High pressure pump with 1 HP motor.
¾ HP shallow well jet supply pump, high and low pressure cut off, motorized ball valves, microprocessor controlled.


In an earlier post I had concerns about sweating copper. With a few tips gathered here, not a single sweated joint leaked. The joints aren’t pretty, but they held.
The 240 GPH Procon pump is undersized for this application. At 150 psi I’m dropping to about 3 GPM across the membranes, which seems too low.
The system is pulling 1.1 GPM permeate @ 150 PSI.

Going to replace the pump for next year with a 330 GPH model.
Should be able to get up to 250 psi and still maintain 4+ GPM over the membranes.
Of course, that can only help increase the permeate flow.

The only real trouble I’m having is a leaking fitting on one of the membrane end caps.
When I initially plumbed everything in, I used a threaded copper fitting to mate to the end caps.

The end cap states to torque the fittings to no more than 65 inch pounds. My torque wrench doesn’t go that low.
Threaded them in finger tight then gave a short bump with a wrench figuring I could always go back and give them another ¼ turn if needed.
They needed it (we’ll call it a pressure washer type leak).

Went to give the first fitting, the one I’m now having trouble with, another twist and felt it give slightly.
My next step was to run to the hardware store to pick up some 2.5” close NPT nipples and replace those copper fittings. Used a flared fitting on the other side of the nipple to pick up the copper.

I borrowed a torque wrench from work (calibrated) to secure the other 3 supply/concentrate fittings to 60 inch pounds…no leaks. The problem fitting, however, got to 50 inch pounds then lost a little torque as I tightened just a touch more, indicating that it may be stripping the threads. About 3 drips per second coming out of that fitting at pressure now. We just put a bucket under it and ran.

Obviously, that leak needs to be fixed, but I’m going to wait until the season is officially over before attempting any repair.

I’m considering a few options and trying to solicit a few more.
I used plumbers tape, maybe dope would be better?
I could JB Weld the fitting in place, with the flared copper connection the nipple would never have to be removed from the cap.

I could drill and tap to the next size up.

As a last resort, I can always just replace the end cap.

Any other thoughts?

[Clinkis]

Those end caps are only about $20. I had to replace one last year that blew off after my pressure got too high (no high pressure switch last year, added one this year). For the price and piece of mind I think I would just replace it. I actually got a spare just in case one gives me trouble.

[maple flats]

I'd get a new cap. I've been told that teflon tape should not be used to seal threads when screwing into any plastic. The teflon is to slippery and you actually get it too tight, torque wrenches aren't true readings then because of the "lube on the threads" causing issues. However, I still use it without issue.
Does anyone use SS hydraulic type fittings? There are some that you just turn in by hand and then turn a nut that pushes an O ring tight to seal. That nut gets turned gently wrench tight, not even 1 grunt.
If you can be 100% sure you get all oil residue off a fitting like that may be just what you want.

[Tweegs]

I bought the housings via e-bay.
Wrote the seller about a replacement cap, still waiting to hear back.

Did you use tape or pipe dope to set your fittings?

edit in: You posted while I was typing Maple Flats.
Pipe dope, got it.
Thanks to you both.

[Flat Lander Sugaring]

Huh, I used Teflon tape and 3000psiNSF these sealant I still have a few drops. The newest end caps I bought seem to be doing better, I only he theb3/4" units I have a stack of 1/2 just sitting probably going to throw out taking up space

oh yea fyi I wrapped my pressure gauge around to 30 so im figuring the vessel are good for 450 psi with no damage :lol:

[Clinkis]

I use Teflon tape and lots of it. I have had no issues with any leaks. Pretty sure this what you need. I know the replacement ones I got were slightly different then the original but they worked fine.

http://www.ebay.com/itm/Beige-95mm-4-Diameter-Reverse-Osmosis-O-Ring-Nylon-RO-Membrane-Housing-End-Cap-/231479134158?hash=item35e53b47ce:g:RVUAAOSw-vlVlf1K

[Tweegs]

Ordered it, thanks for that!
Still haven’t heard back from the original seller.

Hong Kong…oh well.
As long as the other cap doesn’t come apart, we should get through the season.
Favorable forecast starting late next week and running for at least a week beyond.
Buds are still tight.
If all that holds true it’ll save our bacon.

We’re only at about a 25% crop right now.

[Flat Lander Sugaring]

https://www.freshwatersystems.com/p-7052-end-cap-for-4-stainless-steel-housing-34-feed-12-permeate.aspx

[Diesel Pro]

I'd like to see a nice metallic end cap that a guy could get a good tight and secure NPT fit with. I ended up burying the fittings in the caps and they still are not very tight. Like they are tapped too deep. I used lots of tape on mine to get them to seal as well. I do have one style fitting that has a very short threads and a tapered seal that does well. Unfortunately this is just on a push lock adapter and not a full tee etc.

[BreezyHill]

I have one of those beige end caps you can have. Sucks! get the unit to 150 psi and she blows out the vessel. Cheap design. Got in two black units as from fresh water, mean time for a quick fix I drilled and taped the end cap from 1/2" to 3/4". The 1/2 was leaking a tiny bit and then turned to a tiny stream. Took apart and but block thread sealer and all was good. Then the next day the threads failed and the pressure pipe shot out of the threads. Ordered beige end cap and waited for it to arrive. They wont take it back since it was installed.

Sap under pressure gets under the exposed Oring and forces it up with the end cap and out. The tapered design is the issue I think.

Buy the black end caps if you are going over 150...mine is running at 300 right now with no issues. Last season when we had good runs see was at 400.

[Dennis H.]

I had a tough time getting a leak free seal when using the SS fittings in the plastic end caps.
My end caps are for 1/2 NPT.
While working on other things seen the labeling on 1/2" pvc pipe and noted that sch40 is rated for 600 psi! Heck if it can handle 600 psi then my 250 max of the RO should not be a problem and so far it has not.
For the time being I picked up a few 1/2 MPTx 1/2FPT adapters and fit these into the places where I had leaks, then threaded the SS fittings into the PVC fittings, leaks fixed.

Funny thing is even the center fitting which is the permeate outlet leaks, So they will be addressed later when I have time.

[Tweegs]

I’ve been running at 150 psi but only so I could keep over 3 GPM across the membranes.
Yesterday we only had 200 gallons to get through, even the vac wasn’t pulling in any more sap.
Don’t figure on any more sap before the end of the week when we get below freezing again.
(17th to the 24th looks good here, buds probably won’t hold off very long beyond that)

That being the case and since I had an early start, thought I’d chance it.
Gradually took the RO up to 250. Naturally, the leaking fitting got worse, at least it didn’t blow.
Noticed minor leaks develop at the high pressure cutoff fitting, the filter and the needle valve.
The filter was a bit of a surprise, but I guess I can see it. Don’t have the low pressure gauge hooked up yet, not sure what’s really happening on the low side.
Anyway, I’ve got some work to do.

Used the standard white plumbers tape on some of the fittings. Tried the FASTape ™ I heard was all the rage, I wasn’t impressed (expensive, very slippery, hard to work with, didn’t seem to seal any better than the white stuff). Settled on the Oatey grey heavy duty. Though I can’t say I noticed any difference in sealing over the white stuff, it did handle and stay put better. <shrug>.

The beige cap I ordered already shipped, too late to cancel. I’ll return it later.
Did order the black cap from Fresh Water. ¾ supply, I’m currently at ½”…no biggie to adapt.

I think the two biggest lessons here are:
Don’t expect threaded copper fittings to work anywhere on the high pressure side. There’s not enough thread and it’s too soft to get a good bite.

Don’t hard plumb anything with a threaded connection, it’s never tight enough. I threaded a PVC connector to the flow meters then cemented the rest of the PVC in. They leaked, had to cut it off and do it right.:lol: