Hissing Noise from Membrane When Recirculate Pump is On [Old Springtech]?

[cray54]

Tonight, while running the RO, I noticed a change in sound - there is a sound like hissing or the sound water makes when it goes through a barely open valve at high pressure. This sound goes away with the recirculate pump turned off.

[We have an old Springtech RO that has been maintained over the years with various replacement parts, but continues to function. The membrane is only 3 seasons old if I recall, and is regularly rinsed and washed as needed.]

Any suggestions what to look for? I was running some pretty rough sap, but it was going quite smoothly from my perspective just before this issue.

Thank you, Chris

[Bucket Head]

Without seeing your machine, and only going by mine, I'm thinking you must have a bad cup seal (or o-ring?) at the membrane housing end cap or a bad o-ring on the adaptor (if you have those) that goes on the end of the membrane. I've had cup seals leak but I never heard hissing noises. Of course, the machine was running and I would not have heard any hissing anyway! I assume you are hearing it leak-down after the machine is off?

Steve

[cray54]

I'll pull it apart and check the o-rings, thank you for the suggestion. It isn't leaking at all.

I am hearing the sound while the machine is running. If I turn off the recirculate pump, the sound goes away right away. If I turn recirculate back on, it comes back right away.

[Also, each time I try to add a picture here, is says "upload failed", so I couldn't get pictures up readily.]

[Bucket Head]

I have a 30+ year old Airablo R.O., which is basically an older version of Springtech. As I understand it, D&G bought out Airablo way back when, and then also made RO's for Leader. Anyway, I don't know how old yours is or how closely it compares to mine, but I do not have a separate recirculation pump. And the only RO operating experience I have is with this one. Mine makes a hissing sound also, continuously while its running. Thats normal. There is a lot of presuure happening within those components! And it gets louder as you raise the pressure. Mine operates at 475psi, with 550 being the max. However, I have never had it that high. Did your operating pressure increase a little, possibly causing the increase in noise?

Steve

[cray54]

In this case, there was a sudden change (Always listening for new sounds when running equipment, and heard a change and went to check). If I recall correctly, the pressure was higher than usual (It says to run it at 500psi, we run it at 400psi, and I think it was higher). It was challenging to troubleshoot, because I didn't want to cause damage by letting it run, but I was trying to collect information as quickly as possible.

Today, I rebuild the post so I could check the o-rings and seals. Everything looked ok. I cleaned the mating surfaces and reassembled. I ran it for a bit with permeate, and it operated normally.

I think it may have been the cup seal at the top of the membrane as Steve suggested.

[Bucket Head]

Good to hear it's back to normal. Nobody needs extra work or worry during maple season!

Steve

[Bullet]

Thanks for the post Steve. In the off season I sent in my Nano for "repairs". CDL claimed to have made those repairs so the valve no longer hisses. They were wrong as it still hisses. Had they just told me that's the design I would have been fine with it. I've now heard from you Steve and others that perhaps the hissing noise is normal. I'm now looking at the RO bucket kit as there are other issues with my Nano that I'm frustrated with. Frankly I'm reluctant to contact CDL as I've had enough abuse to date.

[Bullet]

I have the Nano 3 Membrane. I also noticed a "hissing" sound coming from the pressure valve at 100 psi. I have tried to get an explanation and/or repair from CDL, but was unsuccessful and was told I have to live with it. Does anyone have a remedy or an explanation?