[chriss]

Tonight I decided to fit my new uprated membrane and restrictor. The current membrane is a 50gpd membrane, ~six months old and the water coming out of the membrane was zero tds, but it was just too slow for my use, so I got a 150 GPD one along with a corresponding restrictor.

Should be a simple job eh? Well, four hours later I'm wet, teasy and had enough of it!

After it was first re-assembled, I left it flush thru a little and then started 'production', after forty minutes or so the membrane output tds bottomed out at 3 before starting to go back up to the mid-teens ?! I stripped it all down and started again, this time it wouldn't go below 7.

Took the tds meter off, waggled it in the vat of RO water made with the previous membrane, 0/1ppm.

Hmm, ok maybe the mains water is totally up the creek tonight, so I measure that and thats coming thru at 109, pretty typical for our place.

Start production again, can't get it down lower than 6 or 7.

I put the carbon block and DI back on and was able to get it down to 1 (looks like the di needs changing), but why can I not get the water out of the membrane lower than this? Are higher rated membranes not so efficient or am I literally just not allowing enough time to flush it thru first time ?

I also think I knackered my tds meter in the process. It's a dual-in-line jobby and one sensor is now reading around 40+ even when they are both put together in tandem, tho when i waggled it in the RO both read 0/1ppm

Oh well, to heck with it all, it's red dead redemption day tommorrow, hurrah!

Chris

Chris

[karnivor]

Membrane quality can vary from manufacturer to manufacturer. Pressure is also important, so make sure that you are maintaining enough flow into the RO unit, so that the pressure is not dropping.
Finally, check your restrictor. These can have a massive bearing on how well your membrane works. It could be faulty or you may even have fitted it the wrong way round.

My RO unit rarely gets below 7 before it goes into the resin and that is with a top make membrane. Such is life.

Most membranes are rated at about 90-95% rejection rate.

Tony.

[chriss]

Well, that makes me feel a littler better, that your membrane output is similar to mine.

I actually measured the restrictor flow too, it's rated 800 ml/min, came out at 760 ml/min. Quality wise, well, got it all from Osmotics which should be pretty good. I'll try and speak to them tomorrow and see what their view is.

Chris

[chriss]

Well, that makes me feel a littler better, that your membrane output is similar to mine.

I actually measured the restrictor flow too, it's rated 800 ml/min, came out at 760 ml/min. Quality wise, well, got it all from Osmotics which should be pretty good. I'll try and speak to them tomorrow and see what their view is.

Chris

[karnivor]

chriss, on May 20 2010, 11:00 PM, said:

Well, that makes me feel a littler better, that your membrane output is similar to mine.

I actually measured the restrictor flow too, it's rated 800 ml/min, came out at 760 ml/min. Quality wise, well, got it all from Osmotics which should be pretty good. I'll try and speak to them tomorrow and see what their view is.

Chris

I'd be very interested in their reply, as mine came from there also.

Here is the spec.

http://www.dow.com/l...w30_1812100.htm
is it genuine?
http://www.dow.com/l.../genuine_ro.htm


They quote minimum 90% rejection.
At 109 going in, that equates to 10.9 coming out.

[chriss]

karnivor, on May 21 2010, 01:01 AM, said:

I'd be very interested in their reply, as mine came from there also.

Here is the spec.

http://www.dow.com/l...w30_1812100.htm
is it genuine?
http://www.dow.com/l.../genuine_ro.htm


They quote minimum 90% rejection.
At 109 going in, that equates to 10.9 coming out.

well after leaving it run all night, this morning it's coming out at 2 to 4, I changed the Di this morning to.

I made a mistake in my post, the actual membrane came from someone else so is probably a different brand.

But the 90% thing is strange, since the membrane I tool out was apparantly doing 100%, maybe I just got lucky.

Oh, and the tds meter seems to be behaving itself now.

Chris

[mikerollins]

hi i just brought a ro unit and when i first terned it on i had great difficulty getting the reeding below 34 when i relised the container is the contaminate, when i measure strait of the pipe it reads 0-00 not bad i think !! my conclusion test the water as its running out of the pipe that way there cant be any ppm !!

[SLAPPY]

mikerollins, on Jul 8 2010, 11:27 PM, said:

my conclusion test the water as its running out of the pipe that way there cant be any ppm !!

That's incorrect, if your filters are shot and if your DI resin has depleted, then there will be a reading (measured in ppm).

What you are referring to is, when you take the reading direct from the hose as opposed to a beaker or anything that can hold your RO water, then there will be no contamination to affect your reading.