RODI/tds

[Salted]

Some questions about rodi. I recently changed my ro membrane. New membrane is same brand and model that was in there, purchased from Amazon. Rodi unit is a BRS 4 stage. Before change tds was at 2ppm. After new ro tds went to 4. Sediment and carbon were changed mid august, and di resin is half depleted per color change. Doubtful I've made more than 75 gal since. The recent change of those and my low water production is what led me to believe it's time to change the few year old ro membrane. Google says discard first 5gal/or 1-2 hours of water production. After roughly 4 hours/25gal of production tds finally dropped to 3ppm. A couple more hours and still at 3. Anyone here experience this? It seems excessive. Might just swap the old membrane back in (which I tried once already and tds went back down to 2).

Next. At what tds are you swapping in new and which filters and what level of tds is your it's not going in my tank point? Even after a good bit of reading on the subject it still remains a bit of a mystery to me. Thanks all.

 

[mwil79]

I swap mine as soon as its not 0 zero tds but I rarely do water changes so most of what its for is top off. Possible that your town added more chlorine to the water or chloromines to combat algae growth?

 

[nvladik]

At which point of the system are you testing TDS? Pre or Post DI?

 

[Yates273]

Also make sure you didn’t install di resin cartridge upside down. Ask me how I know ? Lol

 

[horseplay]

Check the TDS out of the membrane. If it's a few ppm you're good. Mine usually at < 10.

 

[Salted]

I swap mine as soon as its not 0 zero tds but I rarely do water changes so most of what its for is top off. Possible that your town added more chlorine to the water or chloromines to combat algae growth?

Same here. Mostly top off. TDS was at 2, changed membrane and it went to 4. No change in water supply.

At which point of the system are you testing TDS? Pre or Post DI?

Post. The meter on the unit plugs in to the “product” port.

Also make sure you didn’t install di resin cartridge upside down. Ask me how I know ? Lol

Quite sure it’s correct.

Check the TDS out of the membrane. If it's a few ppm you're good. Mine usually at < 10.

I wouldn’t know how to reconfigure the unit to do that

 

[Lola235hgc]

make sure your resin is packed tight it happened to me kept on having a reading of 1-3 until i repacked it

 

[horseplay]

@Salted do you have a TDS meter attached with the RODI unit or you use a handheld one? If you use a handheld one you can disconnect the line to the DI cartridge and measure the TDS there.

 

[nvladik]

Check TDS coming out of the membrane, that's how you troubleshoot the membrane. Try old, try new, see what it says.

 

[Salted]

@Salted do you have a TDS meter attached with the RODI unit or you use a handheld one? If you use a handheld one you can disconnect the line to the DI cartridge and measure the TDS there.

Attached to the unit. I have this one;

Check TDS coming out of the membrane, that's how you troubleshoot the membrane. Try old, try new, see what it says.

As stated, I don’t know how to or if I can reroute the plumbing on the unit to do that. That being said, tds was at 2, replaced membrane and it went to 4, put old membrane back in and tds went right back down to 2. @Lola235hgc , di resin section is packed tightly and hasn’t been touched.

 

[ole farny]

ro/di units are well worth a deep dive imo. it all starts with knowing what's in your water and you should be able to get a report from your water provider to see what's typically in your water. armed with that info, you can customize your cannisters and whole unit based on what you need to remove. it will make your unit and filters more efficient when done right.

modifying your existing unit is pretty easy. first tool to get is a ro tubing cutter which can't be more than around $5 these days, and then some extra tubing if you don't have any. with that, you can add tds meters at the various stages to let you know how it is perfroming. i have and recommend the triple inline hm digital one. i can monitor the tds for the tap water, after the ro membrane and after the di. it helps to let you know what to replace when.

as you have discovered, not or ro membranes are created equal and/or perform the same. same with the filters. do you have chorine only or chlorine and chloramine to filter? once you look at your water and what you have to remove, you can do it better and more efficiently and save money with the right configuration and right filters for the job.

 

[hans24hrs]

I recently replaced all my RO/DI filters and membranes. I had similar issue with new dual membranes. Food some searching it said that they can have a "break in" period. I do a membrane flush before each use (have a T before DI) that I run for a few minutes before water to be used comes out.
Still showing 3-8 TDS with all 2 new membranes, sediment and dual carbon. But shows 0 after triple DI. At this point I am assuming my TDS meter needs to be calibrated. I have also had 0 TDS showing on my ICP RO water tests.

 

[Salted]

I recently replaced all my RO/DI filters and membranes. I had similar issue with new dual membranes. Food some searching it said that they can have a "break in" period. I do a membrane flush before each use (have a T before DI) that I run for a few minutes before water to be used comes out.
Still showing 3-8 TDS with all 2 new membranes, sediment and dual carbon. But shows 0 after triple DI. At this point I am assuming my TDS meter needs to be calibrated. I have also had 0 TDS showing on my ICP RO water tests.

That sounds similar to what I read. The “break in” is the antibacterial preservative they’re packed in being flushed out. I need to disconnect my di resin so I’m not expending it just flushing out the new ro membrane.

 

[hans24hrs]

The best would be to put a T with a shut off valve right after membrane and fish before each use. I'm actually going to move the T I put in to that spot