Jump to content

Don't want to see ads? Become a subscribed member.

Tds Reading After Membranes

charlie tapper

Recommended Posts

depends what you start with, it`s worked out in a rejection percentage, above 95% is good.....



so if you start with 100 your looking for 1ppm to 5ppm with a new membrane... that is 99% to 95%



other factors will come in to play like pressure at the RO and temperature.

Link to comment

Hi Charlie


You haven't given us any detail with regards to what r/o it is. It can't be a Merlin r/o as that would be around 90% when new.


So IMHO your membrane/membranes probably need replacing. If you have one of those RoMan type r/o with several membranes, then it could be 1 membrane that is the culprit. I would try to identify it by coupling up each membrane to work individually and test each one. We were told (by Peter Fogwill) that these type of membranes should work at between 97 - 99% efficiency, anything less than that is wasting resin polishing the water off. This was our experience with a 450GPD 3 membrane r/o we had. Membranes worked at that effieceiency for 6 years before failing. We have now upgraded to a 4040 and that is working at 98 to 99% efficiency and its a year old now.


If they have been in for a while, then I would replace them all anyway.

Link to comment



i brought this one .


only had membranes that were in it for 5 months .


changed membranes from their shop . didnt bring readings down . still read 016.


brought some new membranes from a cleaning store . put them in yesterday brought readings right down to 008


so guessing their membranes were dodgy

Link to comment

Don't want to see ads? Become a subscribed member.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Ad Blocker Detected

Please disable your ad blocker

Our forum relies on ads to pay for the servers and our time maintaining and running the forum.

Sadly running a forum like this is not free, and due to our popularity, we need servers that can handle the amount of traffic and resources our forum uses.


If you do not wish to see ads on our site, please consider supporting the forum with a membership subscription.