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Troubeshoot my RODI issue please

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  • Graeme
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Right, I changed everything out on my RODI, and got zero TDS, however it was running much faster.  I thought it was strange, and checked the TDS after a few days, finding it rose sharply  :umhum:  So, I reordered more cartridges, a new membrane and resin, and I've swapped it all out again.  I've also added an additional dual inline TDS metre, so I'm now measuring the following:
Mains In = 126 TDS
After the sediment and carbon filters = 126 TDS
After the RO membrane = 126 TDS
After the DI resin = 0 TDS

 :|
I'm baffled!  Any ideas?

Mike

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Reply #1

Membrane seal damaged?  Sounds like it was ok to begin with but then came apart with the pressure, now is just bypassing the membrane entirely?
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HK_Fuey

  • Graeme
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Reply #2

Two different membranes in a row?

Mike

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Reply #3

Isn’t there a seal in the housing not on the membrane itself?
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HK_Fuey

  • Graeme
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Reply #4

Yes, good point. It looked OK.  Will be pulling it apart later on, so will check it.

ajm83

  • Andy
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Reply #5

Maybe the raised bit  at the bottom of the housing where the o-rings on the membrane slide into is damaged.
 Did you definitely push the new membranes right into the housing before you tightened it back up? (On mine it has to be flush with the top of the threads.)

HK_Fuey

  • Graeme
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Reply #6

I've spoken to Sam at Vyair, and he's talked through the pipework, and confirmed it's all correct.  He's identified the issue to almost certainly be the flow restrictor.  Apparently, as they need deal with all the dirty water, you can get build up in them after several years.  Mine is about 6 years old, so it's the likely cause.  A new one is in the post.  I'll update once it's installed.

ajm83

  • Andy
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Reply #7

I've spoken to Sam at Vyair, and he's talked through the pipework, and confirmed it's all correct.  He's identified the issue to almost certainly be the flow restrictor.  Apparently, as they need deal with all the dirty water, you can get build up in them after several years.  Mine is about 6 years old, so it's the likely cause.  A new one is in the post.  I'll update once it's installed.

Was the system working prior to changing the membranes?

I don't understand how the flow valve either clogging or flowing too freely could cause what you're seeing.

HK_Fuey

  • Graeme
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Reply #8

If I follwed what Sam said correctly, it's the flow restrictor that creates the pressure build-up in the membrane chamber.

ajm83

  • Andy
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Reply #9

If I follwed what Sam said correctly, it's the flow restrictor that creates the pressure build-up in the membrane chamber.

Least it's a cheap thing to rule out either way.

Gav

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Reply #10


I don't understand how the flow valve either clogging or flowing too freely could cause what you're seeing.

If it chokes all the water would be forced through the membrane taking the dirt with it , if it's not there you wouldn't build pressure to get water through the membrane .

ajm83

  • Andy
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Reply #11

If it chokes all the water would be forced through the membrane taking the dirt with it , if it's not there you wouldn't build pressure to get water through the membrane .

When you say 'forcing through taking the dirt with it' do you mean rupturing the membrane?  That's a good call and would definitely explain the high tds and faster running. 


I assumed Graeme meant the product water was running qiuck, not the waste.  If so then the resitrictor can't be allowing too much through (as in that case just the waste runs faster, and the clean water slows down).



I restricted (but not completely closed off) my waste water line with a ball valve to try and improve the waste:product ratio (don't bother, doesn't work!)  and all it did was slow the output right down, guessing about 50x slower. TDS was still low tho.




Gav

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Reply #12

A lot would depend on the inlet pressure and the contaminants size in the water , larger contaminants may choke the membrane slowing production , while smaller may pass with the build up of pressure beyond its normal operating pressure .


Closing off the waste line may also slow production as the waste water also helps remove contaminants from the outer of the membrane , hence the flush valve on some RO restrictors .

HK_Fuey

  • Graeme
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Reply #13

I have to say, I'm struggling to get my head around how it works, but Sam said it's a holy trinity: pressure in / pump size, membrane gpd rating, and flow restrictor.  If any are out of sync, he system won't work properly.

Thanks:


HK_Fuey

  • Graeme
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Reply #14

Right, still having issues...

I've been on the phone to Vyair a few times now.  First they suggested it could be the the flow restrictor, so I replaced it.  Same problem.

Next, they said it could be the membrane housing was cracked internally.  I bought a new one, which arrived today.  I've installed the new one, and still get the same issue.

I've decided it might help to show you exactly how I have it set up:


Any ideas?

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