Spot Free TDS Increase

[OurTown]

On Thursday we checked our spot free TDS in the bay and it was 20. For the entire time we have owned the wash (5+ years) it has been 10-14. We have an underground poly 1,500 gallon spot free storage tank. I periodically look into the man hole riser cover and it seems like ever since we re-routed the Cat 1010 return line to the tank I have noticed oil floating on top. I'm pretty sure it is from us oiling the pump wicks. Before routing the hose to the tank it was always crystal clear all the way to the bottom. I got the shop vac out and sucked probably 90% of the oil off the top. The pick up for the pump is near the bottom so the oil should not have affected the TDS but Mrs. OurTown thought the return might be churing it up some. It needed done anyway. We turned off the RO system while doing this so it would not kick on. When turning it back on I checked the output hose going to the tank for TDS. When it first kicked on it was about 250 and after about a minute it went to about 13. I thought that was high so I changed the pre-filter since it was due and afterwards it went to 10. Not bad but it seemed to me it should lower if we have about 250 coming in. We shut the wash down and today after re-opening I checked it again at the bay and it is now 24. We check our soft water everyday and it is always 0-1 grains of hardness. Once a week we check the chlorine after the charcoal filter and none has ever been detected. We have never changed the RO membranes so is it time? Why is it going into the tank at 10 (after a minute anyway) but is 24 in the tank? Something strange is going on here.

 

[OurTown]

It is a ProPak 4400 GPD unit.

 

[washnvac]

You may have a check valve bad; pushing some amount of chemical back into the tank. Pull suction tube out of tank, and run each bay individually and see if water/chemical is pushing thorugh that line.

 

[OurTown]

You may have a check valve bad; pushing some amount of chemical back into the tank. Pull suction tube out of tank, and run each bay individually and see if water/chemical is pushing thorugh that line.

I did that and nothing came out of the pump pick up hose or return hose.

 

[MEP001]

It could still be a bad check valve but intermittent. Those are always fun to track down.

 

[OurTown]

We were closed for several days and it got worse after the RO ran. No bay usage. I thought it could be weeping into it but it doesn't look like it.

 

[Roz]

Check your production to reject ratio. Often you can get it down to zero TDS by 2/3 to 1/3 ratio.

 

[MEP001]

Check your production to reject ratio. Often you can get it down to zero TDS by 2/3 to 1/3 ratio.

I like to replumb the systems to run 1:1 and recirculate some of the reject to the pump. The theory is that having the water moving faster through the membrane makes for both a cleaner and a bit more volume of an output.

 

[OurTown]

We pumped the tank down last night from about five feet deep to about a foot. Next time I need to hook up one of those 1 1/2" flexible discharge hoses like what is on a swimming pool pump discharge instead of a garden hose. It would probably only take about an hour with my sump pump then. I put the RO output hose into a bucket and turned the machine on. After a minute or two it was putting out 11 TDS so I put the hose into the tank. That should drop the TDS down quite a bit and hopefully be 15 or less. That should buy us some time to figure things out. After reading the Huron Valley Propak manual I had more questions so I called them and talked to Fred. (IIRC) He did not seem alarmed and said it sounds like it is operating okay. He said the best we could get out of that cold water machine (no mixing valve setup) is around 5 TDS. He also said that we should run the machine longer but with only one on/off float I don't see how that is possible. I argued his point that making the cord longer would not change the run time but would just keep the tank lower. If we replaced the membranes he suggested using some that were more efficient using cold water but I don't see that feature when looking at them. Huron Valley sells the Dow Filmtec ones for about $300 each. We also have some other minor issues: The incoming water pressure gauge is broken and the reject water valve seems frozen. (although it is adjusted correctly) What membranes do you guys use that have a cold water system? We have never messed with the chlorine filter but it looks like it can be manually regenerated. Should we regen it?

 

[OurTown]

Check your production to reject ratio. Often you can get it down to zero TDS by 2/3 to 1/3 ratio.

We have the reject valve set so that we reject about 4% of the water.

 

[OurTown]

I like to replumb the systems to run 1:1 and recirculate some of the reject to the pump. The theory is that having the water moving faster through the membrane makes for both a cleaner and a bit more volume of an output.

Why would they not do that from the factory on an expensive and complicated system like ours? Or maybe it is. I need to look.

 

[OurTown]

If we order new membranes what else might we need as far as gaskets/seals/o-rings?

 

[cantbreak80]

Fred is correct…no need to be alarmed, yet.
TDS above 50PPM will start to show spots so you’ve still got life in those membranes.

Low energy membranes (cold water) are a good solution for increased production.

Short cycling of the RO system…it’s always best to have extended run times for the best quality water. I incorporate 3 float switches in my installations. Low level switch prevents repressurization pump operation. Mid-level switch allows water level to drop approximately 35-40 gallons. High level switch turns off the RO production. Your 3 gpm RO will then run for 15-20 minutes to refill the tank. (I've never been able to do this with those standard corded float switches.)

“Regenerating” your chlorine filter is simply a backwash to redistribute the compacted media and flush carbon fines and debris from the bed. It does not actually regenerate or add life to the carbon. The only true method to determine the media’s effectiveness is regular chlorine testing of the production water. Positive Chlorine tests after a backwash indicate time to replace the media.

Granulated Activated Carbons (GAC) are extremely porous with a large surface. One pound of GAC has the surface area equivalent to six football fields. If your water supplier uses Chloramine for disinfection it’s best to use Catalytic GAC (Coconut Shell Carbon).

Fred will send you all the parts/gaskets/o-rings for your membrane replacement. He might even have the special tools to make things easier, too.

 

[OurTown]

Fred is correct…no need to be alarmed, yet.
TDS above 50PPM will start to show spots so you’ve still got life in those membranes.

Low energy membranes (cold water) are a good solution for increased production.

Short cycling of the RO system…it’s always best to have extended run times for the best quality water. I incorporate 3 float switches in my installations. Low level switch prevents repressurization pump operation. Mid-level switch allows water level to drop approximately 35-40 gallons. High level switch turns off the RO production. Your 3 gpm RO will then run for 15-20 minutes to refill the tank. (I've never been able to do this with those standard corded float switches.)

“Regenerating” your chlorine filter is simply a backwash to redistribute the compacted media and flush carbon fines and debris from the bed. It does not actually regenerate or add life to the carbon. The only true method to determine the media’s effectiveness is regular chlorine testing of the production water. Positive Chlorine tests after a backwash indicate time to replace the media.

Granulated Activated Carbons (GAC) are extremely porous with a large surface. One pound of GAC has the surface area equivalent to six football fields. If your water supplier uses Chloramine for disinfection it’s best to use Catalytic GAC (Coconut Shell Carbon).

Fred will send you all the parts/gaskets/o-rings for your membrane replacement. He might even have the special tools to make things easier, too.

Why did our TDS go from 14 to 24 in a week?
When these membranes go do they go quick or do they creep up?
Our system runs for almost an hour and puts over 150 gallons in the tank per cycle. Could the 250 TDS coming out of the machine for the first minute or two dilute the total total output enough to raise the TDS from 11 to 24? I guess it is math time.
I'll check with my city about what they use in the water for the disinfectant.
What are the special tools?

 

[MEP001]

TDS above 50PPM will start to show spots so you’ve still got life in those membranes.

That's what the manufacturers say, but in my experience you'll start seeing spots above 30 PPM. Mine is up to 34 and there's very light spots left behind.

The only true method to determine the media’s effectiveness is regular chlorine testing of the production water.

I test the RO reject water for chlorine. The system will concentrate it and will show up easier. Some municipalities use so little chlorine that it will barely show up on a pool/spa tester, so if you test for it once a week at the reject you're going to spot it sooner.

 

[MEP001]

Why would they not do that from the factory on an expensive and complicated system like ours? Or maybe it is. I need to look.

For some I believe it's ignorance, or possibly cost savings. The cheapest system I've seen is wired against electrical code and uses one leg of 240V run through a float switch with the other leg wired live all the time to the motor. It works, but it's not proper, and with the way it chatters the motor every time it comes on it reduces the pump motor life. There's a pressure switch that has a restrictor to prevent the motor from having to start and re-start multiple times, but it's $10 more so they don't use it. A regulator or a second adjustment to make it run 1:1 costs money so they don't do that either, they don't care that it costs you on your water bill.

 

[OurTown]

Super Wash told me that anything above 35 can spot black cars. We sure are creeping that way faster than I would like. I would like to keep it as low as possible without going to extremes in order to buy us time to resolve issues like we have now.

 

[washnvac]

Fred is correct…no need to be alarmed, yet.
TDS above 50PPM will start to show spots so you’ve still got life in those membranes.

I see slight spots on my black vehicle above 20ppm. Therefore, I change my membranes when tds approaches 20 ppm. It is the final rinse; too important not to have right.

 

[Roz]

Wow we change our prefilter when the TDS gets to 3 or every 150 Hours.

 

[MEP001]

Wow we change our prefilter when the TDS gets to 3 or every 150 Hours.

The prefilter shouldn't affect the TDS.