High TDS with New Install

[Tech Savvy]

I recently purchased and installed an under sink RO system. However, even after several weeks of use and countless flushes, the TDS of the filtered water is really high. The system is from Express Water.

It's a 5 stage system that has a 50 gpd membrane.
Well water at the tap is 850 ppm.
Filtered water is 180 ppm.

So, the rate of rejection is quite low for an RO system from what I understand. I have flushed every filter, checked the waste water drain, all hoses are connected correctly... it's a pretty dummy proof system. The membrane is seated properly too, I've checked many times.

I'm at the conclusion that the included membrane is cheap junk. The system itself is all "off the shelf" parts. Everything is standard size and standard fit. The only thing I am unsure of is the quality of the included filters, which they are practically giving away. My guess is the membrane is just a poorly made product. I tried to inquire where they source them from, but they seem to be completely unbranded.

I recently purchased a Filmtec 75 gpd filter and matching flow restrictor. I figured a name brand membrane would be my next step in trouble shooting. That will arrive later today and I will give it a shot. Any other suggestions are welcome in case the new membrane doesn't solve my problem.

[JonnyBoy]

That's a very high ppm to start with? Can you replace anything post membrane with another membrane, I would use two instead of one. See if that helps.

[kesavan]

First of all check input water pressure. otherwise the membrane may be defective. I think there is no other thing for such high tds.