Water Softeners and Air Filtration Systems - RO System pulling cold water to drain

I have a Culligan RO System. When I turn off the cold water to the faucet, I still hear water draining. It seems the siphon valve on the cold water line that goes to the RO System is open and pulling water (venturi effect perhaps?) that just runs back to the drain pipe under the sink. Does the inline valve need replacing or is it being caused by the RO System. The red light is not on indicating a need for a filter change. Any advice would be appreciated of where to start. Thanks!

I have a Culligan RO System. When I turn off the cold water to the faucet, I still hear water draining. It seems the siphon valve on the cold water line that goes to the RO System is open and pulling water (venturi effect perhaps?) that just runs back to the drain pipe under the sink. Does the inline valve need replacing or is it being caused by the RO System. The red light is not on indicating a need for a filter change. Any advice would be appreciated of where to start. Thanks!

Where are you turning 'the cold water off at the faucet'? Under the sink? Is that shut off before or after the RO lead line?

Sounds normal to me..RO systems "use" water to "make" purified water. For every gallon of purified water produced, a certain ratio of "regular/dirty" water will be used to clean the membrane and discharged back to the environment via the drain.

Since RO systems produce water slowly, it is not uncommon to have a storeage tank under the sink that is slowly filled by the RO with purified water. Each time you use water, the tank pushes water to the faucet and then the RO many run for hours (depending on how much water you used) to replenish the tank.

Most well-made RO systems produce around 50gpd, but there are some out there that only make 10gpd, so if you extrapolate the math it could take anywhere from a half hour to as long as 2.5 hours to replenish a 1 gallon tank if your influent water is "warm" (70 deg F). As the inlet water temperature decreases, the membrane flux rate drops. If your inlet water is as cold as 40 deg F, your flux rate is only about 35 - 40% of maximum, so your fill time increases proportionately.

Observe how long you hear water "running" after you draw down the entire tank and report back, with the model of your RO and can advise if this is running inordinately long or if it is normal.

Good Luck !

Greg Reyneke CWS-VI

what type of culligan RO system do you have? I have just purchased the Aqua-Cleer advanced and was wondering how you liked it.
thanks

Most well-made RO systems produce around 50gpd, but there are some out there that only make 10gpd, so if you extrapolate the math it could take anywhere from a half hour to as long as 2.5 hours to replenish a 1 gallon tank if your influent water is "warm" (70 deg F). As the inlet water temperature decreases, the membrane flux rate drops. If your inlet water is as cold as 40 deg F, your flux rate is only about 35 - 40% of maximum, so your fill time increases proportionately.

Greg Reyneke CWS-VI

Greg makes excelent points here. Be careful about ads that claim ""100gpd"" for their systems. In addition to the temperature of influent water, two other aspects must be calculated when determining RO production given the membranes are the same size and type. The TDS and water pressure also affect permeate production. The lower the TDS and higher the pressure, the better the production.

Although the Culligan RO is a proprietary unit (special filters, etc.), it really offers nothing remarkable and its technology is standard, at best. If you look at their websites, they rarely mention any special features and just talk about the advantages of what any generic RO can provide. They do have a wide filter selection for customizing it premium unit.

Andy Christensen, CWS-II