RO question

[rcb]

Hello, I have set up a 5 stage RO system to get me through the dry months. Basically I have it so it doesn't go all the time, just when my water barrel gets below a certain level.

The problem is it doesn't seem to be able to get below 90 TDS. Total gallons so far are about 2000. I don't think the filters or the exchange should need to be changed yet should they?

When it has been off for a while, I do run it for at least an hour first before capturing the water.

Some numbers.

My well water - between 700 - 900 TDS.
First water out after I turn it on - between 120 - 180 TDS
After running for roughly an hour - about 110 TDS
After running overnight - -90 - 100 TDS

Additionally, I can still smell the sulfer in the RO water. It's not as strong as the water from the hose, but it is definitely noticeable.

Yes I just checked my TDS meter, it's seems to be working fine.

Any suggestions?

Renee

 

[Ray]

Depending upon the membrane used, the rejection can be rated anywhere from 92%-99%, meaning that you should expect to see your outlet TDS to be somewhere below about 70 ppm. However, as it isn't, it sounds like you might be getting some leakage past the membrane seals.

There are two o-ring seals at the outlet end of the membrane (the part deepest in the housing), and a "collar" seal at the inlet end. If either of them has a crimp or tear in it, some of your inlet water could be bypassing it and mixing with the pure.

I suggest a trip to your local hardware store and pick up a small tube of silicone grease. Remove the membrane from the housing, liberally coat the seals, and reinsert it.

 

[NYEric]

Well water 700-900 TDS.. I think we found the problem.

 

[orcoholic]

I used to have a small system where you could adjust the amount of "good" water that's produced. The less good water the system produces, the lower the TDS. The downside is that the amount of wastewater is increased and thus you need more water going through the system.

There may be an adjustment that allows you to slow down the amount of good water produced. I can't remember where it was, but I think it was at the top of outlet tubing (where the good water tube it comes out of the membrane).

 

[Ray]

Most modern systems have a fixed-volume restrictor on the flush water exit line, usually sized to permit 3x the rated pure water output volume. For example, a 100 gpd system will have an 800 ml/min restrictor (100 gpd = 263 ml/min, 800/263=3.04). Most of the systems I have sold recently are closer to 2:1, my own system is 1.25:1, and it has no significant impact on the purity of the water passing through the membrane.

 

[dodidoki]

Hello!
I think there must be something very big problem....my tap water is from calcareous caves and VERY hard, measured with TDS meter is about 275-300 ppm. I use my RO system with ion changer filter, it changes ca/Mg to Na and RO filter have to remove only Na , so this way Ca/Mg does not make RO membrane wrong. I only have to change ion change tube but it is much cheaper.

My RO water is about 6-8 ppm, and 25-30 ppm if membrane begins to get tired.

 

[ALToronto]

Sounds like you need two of these systems in series. Or from what I understand, a water softener will not harm the RO membrane, so that may be a solution for you.

With 700 ppm, you must be replacing the seals and flaps in your toilet tanks very frequently, and you risk overheating your hot water tank due to scale buildup.

 

[rcb]

Thanks Ray, I will try that. Or learn to live with it.


Dodidoki, I'm relatively positive the TDS meter is correct, as I test it regularly against known concentrations.

AlToronto, no, we don't have that problem. The house is on a water softener. I can't put the RO system on it without some major plumbing issues, which I'm not willing to do, or have hoses running everywhere.

Up until recently, there has been enough rain to dilute the water as I use it, and hopefully we will get some more soon.

 

[keithrs]

Are you flushing the membrane after use? If not, with that high of a TDS and amount of water you have used may have fouled the membrane. Also membranes can foul if you let them go dry. I would recommend replacing the membrane since there under $35.

 

[Rick]

Hello!
I think there must be something very big problem....my tap water is from calcareous caves and VERY hard, measured with TDS meter is about 275-300 ppm.

Ground water in lots of Florida would put your wimpy water to shame Dodidokioke:

Some inland places in Florida even have sea water infiltration that make RCB's 700mg/L look positively fresh!

Surface waters in the desert SW of the US also frequently tip the 700mg/L mark. And desert sinkholes can be saltier than the ocean.

 

[NYEric]

The water table in Florida is very screwed up. They are using water that shouldn't be bothered; that is why sinkholes are so prevalent. If you look at a map of Fla, like around Ococee or Winter Haven you see lots of little round lakes that are really perfect sinkholes.