[Smudger]

Morning chaps,

Had my Merlin RO for just about a year now, changed the pre filter approx 4 months ago,  all has been ok until a few days ago,    the TDS has crept up from 17 to 50 - and i cant get it down,  this is not TDS creep as is starts from 180 then drops after 3 to 4 mins.

I use a booster pump so flow is good.  Dont think it's the pre filter as the flow rate is still good.

Would you think the membranes require changing ? - they are a year old and looking at the web sites they should last between 2 and 3 years. 

i make on average 400 ltrs per day - 5 days a week,   any hints/help tips to try before buying new membranes

cheers

Darran

[G Griffin]

 You could check for a tds rise in your water from the tap. This could be a factor but that does seem a big increase.

[Smudger]

Tap TDS pretty steady at 320  - went up in the winter months to 380 so not that.

Darran

[formb]

I have a Merlin. It's always on.

2-3 years is I suspect if you are using it for drinking water purposes.

I change mine every 3-6 months.

P.S My tds does not go up. Production rate just goes down.

[Paul Coleman]

Morning chaps,

Had my Merlin RO for just about a year now, changed the pre filter approx 4 months ago,  all has been ok until a few days ago,    the TDS has crept up from 17 to 50 - and i cant get it down,  this is not TDS creep as is starts from 180 then drops after 3 to 4 mins.

I use a booster pump so flow is good.  Dont think it's the pre filter as the flow rate is still good.

Would you think the membranes require changing ? - they are a year old and looking at the web sites they should last between 2 and 3 years. 

i make on average 400 ltrs per day - 5 days a week,   any hints/help tips to try before buying new membranes

cheers

Darran

From reading your post in a bit of detail, I might be able to have a stab at this one.
Firstly, Merlins aren't the cleanest of ROs as I'm sure you know, so a TDS after RO in the 20s or 30s isn't so unusual as the membranes age.
Maybe the membranes are having a shorter life because you left it 8 months before changing the pre-filter.  Really, it shouldn't be left any more than 6 months between changes (3 months for 10" pre-filters).  Some people say even less than that though I've always been OK at 6 monthly changes.
Also, I note that you say pre-filter rather than pre-filterS.
Now I don't know what setup you have but mine is a freestanding 20" sediment filter followed by the merlin unit with three housings.  Housing one is a carbon/chlorine filer.  Housings 2 & 3 are membranes.  Is it possible you are only using the one pre-filter (carbon/chlorine) that is part of the merlin unit?  If so, I suggest that if you need to change the membranes, you install a sediment/debris pre-filter before the merlin unit.  I also have an iron pre-filter before everything else but this is not usually necessary.  Indeed I only installed it because there was a higher level of iron in the water following flooding several years ago so I change that about every 18 months just in case.

[Smudger]

Paul - thanks for this info -  the answer is yes i just have the merlin with the 3 housings so just the carbon pre filter.

so if i get another pre filter what am i looking for and what do you put in it ?

form B - you change the membranes every 3 to 6 months or the carbon pre filter ?  thats when the production rate drops for me - and i changed it ( carbon filter change is stated 6 to 12 months )

Darran

[Paul Coleman]

Paul - thanks for this info -  the answer is yes i just have the merlin with the 3 housings so just the carbon pre filter.

so if i get another pre filter what am i looking for and what do you put in it ?

form B - you change the membranes every 3 to 6 months or the carbon pre filter ?  thats when the production rate drops for me - and i changed it ( carbon filter change is stated 6 to 12 months )

Darran

Before the merlin unit, I have a vessel that contains a 20" sediment pre-filter.  The vessel is a bit larger than the merlin housings as the items they contain are only about 17".  The sediment filter looks a bit like the carbon filter but is white in colour (the carbon/chlorine filter in the merlin housing is grey as I imagine you have noticed).
if you look at:
http://www.gardinerpolesystems.co.uk/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2egardinerpolesystems%2eco%2euk%2facatalog%2fWater_Treatment%2ehtml&WD=filter&PN=Filter_Housings%2ehtml%23aRO_2dFIL_2dWRENCH_2d20#aRO_2dFIL_2dWRENCH_2d20

go to the third picture down (blue 20" filter housing).  That's the sort of housing I have.
Alternatively you can have a 10" one but they need to be changed more frequently.  Some people also recommend an additional pre-filter called GAC carbon.  Never done that myself though.
The filter you want for sediment I believe is a 5 micron sediment filter.  Gardiners do them as per the above  link.  I usually get mine from Omnipole as it's more convenient for me to collect than to receive deliveries.

I'm no techie whizzkid but I suppose it's just possible that your merlin carbon filter may be getting clogged sooner due to it taking the brunt of the sediment.  I may well be wrong.
What I will say is that I have never used an RO without a sediment pre-filter.  My merlin readings are on the climb too but that's partly because I use a waste restrictor due to being on a water meter.  But your's seem to have climbed too high, too soon.
It may be that it's nothing to do with the absence of a sediment filter.
I'm sure someone on here could give you a more definitive answer than I can.
Just to add that I find John Guest fittings more reliable  on housings.

[Paul Coleman]

Just to clarify:  I change the 20" sediment pre-filter and the merlin carbon/chlorine pre-filter every six months.  Never more than a week longer but I'm a bit picky like that.

[Smudger]

Cheers Paul,  just been looking at my records and i did change the pre filter at 6 months - more or less on the dot so this one is actually older than i thought   :  at 5 months and 1 week.   my water production is a good 40% higher than the first six months i had a Merlin.

I will get another carbon filter fitted on friday. and look at getting an extra pre filter - 5 micro good enough - i have seen 1 micron filters - or would that cause problems?

i can't put a def. time on the rise as i got a little lazy and once the TDS hit 30 i just hooked upto the resin!

thanks for all the info.

Darran

[Paul Coleman]

Cheers Paul,  just been looking at my records and i did change the pre filter at 6 months - more or less on the dot so this one is actually older than i thought   :  at 5 months and 1 week.   my water production is a good 40% higher than the first six months i had a Merlin.

I will get another carbon filter fitted on friday. and look at getting an extra pre filter - 5 micro good enough - i have seen 1 micron filters - or would that cause problems?

i can't put a def. time on the rise as i got a little lazy and once the TDS hit 30 i just hooked upto the resin!

thanks for all the info.

Darran

I think 5 micron is the norm but check with your supplier to make sure.
If the water production is higher than it was before, that's not a sign of membranes going kaputt.  Normally, membranes being knackered are indicated by a sharply rising TDS and a sharply declining volume of production.
However, if 50ish TDS can't be improved upon by tinkering, maybe it's nearing the time to change the membranes anyway.

[Smudger]

Going to change the pre-filter first to see what happens.
hopefully this works a it's the cheap option then getting another pre-filter fitted.

darran

[Smudger]

changed pre-filter - TDS back down to 22 ( not as good as new but happy with that ) 

also found some info buried in the manual - if your producing more than 20 gallons a day you should have an additional pre-filter   

i think that should be made clearer when buying! - still got one on order so will install next week, 

Also flushed through a dose of chlorine bleach and wow,  what a load of crap came out of the waste !!

still all smells fresh and clean 

Darran