tds meter

[Evolley1]

So I have a inline TDS meter hooked up to my RO unit which is then hooked up to an auto topoff float valve to the tank. My question is...in order to get a proper reading from my TDS meter does the output flow have to be fast? It seems as though if I decide to fill a bucket with fresh RO my readings seem to be at 0 or 1. When I just allow it to topoff the readings are around 9-11. It doesn't make much sense. The topoff is fairly new, same thing goes for all of my filters. Any toughts?

 

[Doubledown]

Each time your RO unit shuts down there is water left in the chambers. For lack of a better term, this water doesn't get completely "processed" upon the start up of the unit. It usually takes a few (say 30 to 60) seconds for the water to clear/flush the membrane and filters before the unit provides fully processed RODI water. This is why it is recomended that each time you re-start the unit, you let the water run for a minute and not to use this "partially processed" water.

What happens when you connect it directly to your tank is that the float valve will turn the RODI unit on and off several times per day for very short time periods - never really clearing the filters. What it does is send the partially processed water that has been sitting in the unit to your tank. This water has a higher TDS that your meter is reading.

I have been told that it is better to manually turn on the RODI unit to fill a larger resevoir and use that water to top off the tank. Once this resevoir is full you turn the unit off until it is empty then start it up again. For what it is worth, I have my RODI unit connected to a 44 gallon trash can with a float valve in it and a drain line at the bottom that runs to another float valve in the sump (water is topped off via gravity because this can is raised about 2 feet above the sump level). The resevoir usually lasts about a week and I turn on and off the RODI unit to fill the large resevoir. Each time I do I open the flush valve on the RODI and flush out the membrane for a minute or 2 before using the water.

 

[Rod Buehler]

<a href=showthread.php?s=&postid=7593339#post7593339 target=_blank>Originally posted</a> by Doubledown
Each time your RO unit shuts down there is water left in the chambers. For lack of a better term, this water doesn't get completely "processed" upon the start up of the unit. It usually takes a few (say 30 to 60) seconds for the water to clear/flush the membrane and filters before the unit provides fully processed RODI water. This is why it is recomended that each time you re-start the unit, you let the water run for a minute and not to use this "partially processed" water.

What happens when you connect it directly to your tank is that the float valve will turn the RODI unit on and off several times per day for very short time periods - never really clearing the filters. What it does is send the partially processed water that has been sitting in the unit to your tank. This water has a higher TDS that your meter is reading.

I have been told that it is better to manually turn on the RODI unit to fill a larger resevoir and use that water to top off the tank. Once this resevoir is full you turn the unit off until it is empty then start it up again. For what it is worth, I have my RODI unit connected to a 44 gallon trash can with a float valve in it and a drain line at the bottom that runs to another float valve in the sump (water is topped off via gravity because this can is raised about 2 feet above the sump level). The resevoir usually lasts about a week and I turn on and off the RODI unit to fill the large resevoir. Each time I do I open the flush valve on the RODI and flush out the membrane for a minute or 2 before using the water.

Good post! And another reason that (IMO) having your RO plumbed directly to your tank is a bad idea. There are many companies that set the systems up with the RO plumbed directly to the tank :rolleye1:

Not to mention the fact that they can fail and pump too much fresh water into the system. Just last week a customer had a skimmer over skim and unfortunatley he had his skimmer going to a drain instead of a collection container/auto shut off container. As the skimmer was pumping fresh water out the RO was pumping fresh water in.

 

[Doubledown]

Thanks Rod - see I do listen when you tell me things .

 

[Evolley1]

So does this mean that my RO water will always be a higher TDS reading if I don't stop the unit. Or is the meter just off. By having an open top and it being summer it seems as though my auto topoff is constantly dripping into my sump. I have a 2gal reservoir tank after my RO followed by a small rubbermaid 1gal container w/ a floatvalve that then gravity feeds into my Kalk reactor. After the reactor it goes into the sump via float valve. If I had room I would have a larger reservoir so that I could turn the RO on and off. In this case I don't but should I still turn it off anyway? I would have to do this daily in order to keep up with evaporation since my 2 gal would probably drain. I have a separate line with a valve that I use to fill a bucket for water changes that I could use regularly to flush the system. That may be my only option to flush my membrane. I still don't get it though. If the unit is constantly in use why are the readings higher than they are supposed to be???