High TDS in RO water

[NanoTanker]

I am in the OKC area and wondered if anyone was having issues with higher TDS in their RO water prior to sending it into a DI canister. I have a Typhoon III with new pre filters (sediment, catalytic carbon, and a carbon block) and a new 75 gpd membrane. I cant get any better than 29 off a tap of 450. Pressure should be ok at 52 psi since I took the unit over to a family members house with a pressure of 64 and the relative rejection rate was consistant with what I am seeing. Temp is coming in off the cold line around 79*.

I am aware that ammonia will need to be eaten up from the chloramine breakdown but I don't know if the TDS meter is seeing the ammonia as ionic or not after the breakdown of chloramine.

I might be expecting too much out of my new RO membrane?

 

[deleau]

What part of the city are you in (i.e. where is your water from)? The city has data on their website (and they send out information in your bill once a year or so) regarding what's in the water. If you matched that up with your readings, you might be able to gauge whether you may have an issue with your plumbing.

I do not think you are necessarily out of whack; I have some Sonic drive-ins as customers around town, and they all have RO/DI systems for their ice/drink machines. Depending on where they are in town, the pressure will vary wildly.

And as far as I understand, a TDS meter does not measure ammonium (NH4+).

 

[NanoTanker]

Both houses are supplied by Lake Hefner so I knew that it wasn't the best experiment but it was what I had available to me over the weekend. I am just surprised I guess since I changed my old membrane which was 4 years old and the TDS really didn't improve. I will look for an old bill when I get home this evening for that water report. Is it any different than the published one online?

I don't even know if ammonium is produced from the breakdown of chloramines. That was just an idea that came to mind since I thought TDS meters picked up charged particles within a water sample.

 

[deleau]

It's not usually on your actual bill; it's an insert that comes along with the bill. TBH, I think Hefner is one of the better plants. IIRC, Draper is usually the worst although none of them are considered "bad" for human drinking purposes.

I know what you are thinking in regards to the TDS meter. I looked at the reference material, and it just lists/discusses ionic salts and minerals not dissolved ammonia/ammonium or chlorine.

As long as your DI canister is able to get your TDS to 0, then I wouldn't worry too much...we know OKC water isn't the cleanest, so...

 

[NanoTanker]

I did make a gallon or so of DI water once everything was flushed. I got 0 TDS from both of my stick meters. I will keep track of my water production and life of the DI canister for reference sake.