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Nameless Drudge

  • Posts: 997
Why does flushing a membrane make any difference?
« on: April 27, 2012, 10:35:46 pm »
I flush my membrane by having the waste tap fully open.However a tiny amount of pure is still produced as this is happening which just dribbles out.I cant work out why flushing in this way makes any difference at all.
 Can someone explain ?

dave f

Re: Why does flushing a membrane make any difference?
« Reply #1 on: April 27, 2012, 11:04:39 pm »
ive just been to a supliyer who showd me a membrain that had not been flushed and the build up of crud was amazing considering it is expensive to replace its best to flush on a regular interval, imo

Nameless Drudge

  • Posts: 997
Re: Why does flushing a membrane make any difference?
« Reply #2 on: April 27, 2012, 11:19:38 pm »
So possibly then, the faster water flow might dislodge crud build up on the outer of the membrane which would be hard water deposits at a guess but as a tiny bit of pure is still produced then isnt the membrane spending time working and filling with tds as its flushing so i`m not sure of a benefit,maybe it should be taken out and scraped clean.

mikecam

Re: Why does flushing a membrane make any difference?
« Reply #3 on: April 27, 2012, 11:22:18 pm »
I flush my membrane by having the waste tap fully open.However a tiny amount of pure is still produced as this is happening which just dribbles out.I cant work out why flushing in this way makes any difference at all.
 Can someone explain ?
This might be long winded and i make no apology for explaining the bits you already know, here goes..........
(i'll try keep it short!)
 A filter works pretty much like you imagine it does water goes in one end then through the filter and out the other end, the sediment/particles or whatever the filter is restricting does not get through and stays in the filter. You replace your filter when it becomes full/clogged.
 A membrane does a similar job to a filter, your water goes in to it but where it differs is that it has two ways out. One way out is through your waste pipe and the other way out is through the membrane and out to your product line. The water rushing across/through your membrane housing and out to your waste will take all the particles off the face of your membrane and out to your waste line  thus keeping your membrane 'clear'. Over time some particles/contaminants do build up on the membrane, by opening up your waste you are 'restricting' what is 'forced' through the membrane. The hope is the passage of water going mainly to waste will carry away most of the contaminants/particles with it. Thereby keeping your membrane clear.
 A properley used membrane lasts about five years. The reason for this is that the membrane itself breaks down after this age. If you never flushed then contaminants would just build up on it and it would 'clog up' alot sooner.
Flushing at a lower pressure can eliminate any 'product' water going through the membrane.

mikecam

Re: Why does flushing a membrane make any difference?
« Reply #4 on: April 27, 2012, 11:23:53 pm »
maybe it should be taken out and scraped clean.

I think they're made from TFC (thin film cellulose, or summat like that) scrape them and you'll disintegrate it !!!

Ian101

  • Posts: 7889
Re: Why does flushing a membrane make any difference?
« Reply #5 on: April 28, 2012, 08:08:13 am »
whats your new 4040 like from Vyair ?

have u a link to it ?

Dave Willis

Re: Why does flushing a membrane make any difference?
« Reply #6 on: April 28, 2012, 08:10:43 am »
I took an old one apart once. It's a tightly wound roll of plastic looking sheet with microscopic holes in it. Even flushing won't clear all the sufaces but it helps.

Spruce

  • Posts: 8681
Re: Why does flushing a membrane make any difference?
« Reply #7 on: April 28, 2012, 08:48:19 am »
I flush my membrane by having the waste tap fully open.However a tiny amount of pure is still produced as this is happening which just dribbles out.I cant work out why flushing in this way makes any difference at all.
 Can someone explain ?
This might be long winded and i make no apology for explaining the bits you already know, here goes..........
(i'll try keep it short!)
 A filter works pretty much like you imagine it does water goes in one end then through the filter and out the other end, the sediment/particles or whatever the filter is restricting does not get through and stays in the filter. You replace your filter when it becomes full/clogged.
 A membrane does a similar job to a filter, your water goes in to it but where it differs is that it has two ways out. One way out is through your waste pipe and the other way out is through the membrane and out to your product line. The water rushing across/through your membrane housing and out to your waste will take all the particles off the face of your membrane and out to your waste line  thus keeping your membrane 'clear'. Over time some particles/contaminants do build up on the membrane, by opening up your waste you are 'restricting' what is 'forced' through the membrane. The hope is the passage of water going mainly to waste will carry away most of the contaminants/particles with it. Thereby keeping your membrane clear.
 A properley used membrane lasts about five years. The reason for this is that the membrane itself breaks down after this age. If you never flushed then contaminants would just build up on it and it would 'clog up' alot sooner.
Flushing at a lower pressure can eliminate any 'product' water going through the membrane.

That's it in a nutshell. Good explanation Mikecam.

I have found that with my 450GPD i still get a small 'leak' through the membranes on flush so still do produce. I remember once opening the flush valve and forgetting it. When I got back to my system later I couldn't understand why the R/O had produced so little water until I realised my mistake. The waste pipe from my R/O discharges into the bathroom drain, and the wife has taken it upon herself to monitor the amount of waste water incase it happens again.

Spruce
Success is 1% inspiration, 98% perspiration and 2% attention to detail!

The older I get, the better I was ;)

Pureclean Essex Services

  • Posts: 186
Re: Why does flushing a membrane make any difference?
« Reply #8 on: April 28, 2012, 01:14:48 pm »
I always flush the RO weekly for about an hour with booster pump on,but daily before I start filling tank with pure water,I disconnect hose from DI and let the pure water run for about 5 minutes,just until TDS has dropped then reconnect and start filling tank,but mainly I think you should change pre filters on a regular basis as these are the first in line,and also the cheapest to replace.

Regards Brian.

[GQC] Tim

  • Posts: 4536
Re: Why does flushing a membrane make any difference?
« Reply #9 on: April 28, 2012, 04:23:35 pm »
I flush it before every fill for about 8-10 minutes, this also to remove air in the housing. If your membrane isn't wetted properly it can cause damage as well.

dave0123

  • Posts: 3553
Re: Why does flushing a membrane make any difference?
« Reply #10 on: April 28, 2012, 05:47:37 pm »
I got told by June at gaps water not to flush your membrane with a boosterpump on.. just usual tap pressure
Dave.

Nameless Drudge

  • Posts: 997
Re: Why does flushing a membrane make any difference?
« Reply #11 on: April 28, 2012, 07:15:23 pm »
I`m on a meter,with the water cost factored in it must be a borderline call whether to flush regularly or just to replace the membrane.
 

traps7

Re: Why does flushing a membrane make any difference?
« Reply #12 on: April 28, 2012, 08:12:58 pm »
I flush after for about 4 or 5 minutes after every 1000 litres of pure I make. And that'll probably be with hard water because by the time I've made 1000 litres my softener would probably need regenerating.

mikecam

Re: Why does flushing a membrane make any difference?
« Reply #13 on: April 28, 2012, 09:25:32 pm »
I`m on a meter,with the water cost factored in it must be a borderline call whether to flush regularly or just to replace the membrane.
 
I think it was Vin from Perfect Windows that alerted me to the obvious......if you run the RO producing less waste and thereby shorten its life it may still be cost effective to operate this way. Same with flushing, just do a short flush , don't overdo it if you're on a meter.

Dave Willis

Re: Why does flushing a membrane make any difference?
« Reply #14 on: April 28, 2012, 10:35:39 pm »
It's only about £2 for 1000l  ???

Pureclean Essex Services

  • Posts: 186
Re: Why does flushing a membrane make any difference? New
« Reply #15 on: April 29, 2012, 10:09:01 am »
I got told by June at gaps water not to flush your membrane with a boosterpump on.. just usual tap pressure

Cheers Dave I'll try this on my next flush,just thought with booster on,more pressure,better results.My tap pressure is only around 32PSI,might try tap pressure and extend the flush time to around 1 1/2-2hours.

Regards Brian.