membrane housings

[darkmachine]

I have two 40" stainless steel 4040 membrane housings and just dropped two new membranes in after cleaning. I build pressure to about 100 psi and then it drops. checked the o-rings on the permeate ports, all good. I'm wondering if i have deformed the housings by tightening the end cap holders too much, is that a thing? the housings were not very expensive but I've never had any trouble with them in the 3 years I've used them. If anyone else has encountered this let me know.

[darkmachine]

Well I think I finally diagnosed the issue. Upon close inspection it looks like the lip of one of my end caps is cracked. I replumbed the RO to use a single membrane excluding that cap and voila! It builds pressure and works just fine. My thinking is that the cracked lip allowed the end cap to slip up just far enough so that it no longer engaged the tube where the permeate flows out of the membrane. Anyway up and running, in caps are cheap may not have one in time for this season.

[MarquisVII]

Glad you figured it out. These end caps are the worst. I have 4 broken this year and a one replacement just arrived with about 6-7 hairline cracks all throughout. Unreal. Amazon/ebay only have junk. Need to pay up for the *slightly* better quality ones and cross your fingers they won't crack before your fittings are torqued enough to not leak. I'm going to try Block thread sealer next.

I think I've noticed that the caps that have the max torque spec embossed on them seem to be better than the ones that are smoother and don't have any markings on them.

[darkmachine]

I think I might be shopping for two codline vessels after the season is over. I have two composite vessels I could use but they are for 2.5x40 membranes, which are just as expensive as the 4" ones.