View Full Version : RO system - Solenoid question

08/21/2016, 06:32 PM

I've purchased 4 solenoids, an arduino, 12v PSU, a relay board and 2 float switches. I've got an arduino program setup to automatically fill my water barrel whenever the low water float switch engages.

Right now I have 2 solenoids for the product water and 2 on the waste water. They're setup as the following:

Waste1 - Bypass the flow restrictor to flush membrane
Waste2 - Normal waste line through restrictor

Product1 - Dumps into drain to flush out TDS creep water from the membrane (in excess of 120TDS after sitting for 24hrs)
Product2 - Normal operation emptying into the barrel

When the float first triggers the program, the flush and dump solenoids open for 20secs to allow the system to clean itself. They then close and the normal operation solenoids open to allow the barrel to fill.

My question is: Do I need a 5th solenoid on the main line feeding the RO system? When the system isn't running, all 4 solenoids will be closed, stopping all flow through the lines. I'm worried that the pressure from the main line will cause leaks/blowouts on the filters/membrane/DI stage if it can't vent out. My water pressure varies between 65-75psi on a 1/2" municipal feed pipe. Can the fittings/canisters deal with that pressure?

When off, it would be a similar situation as those who use 'auto shutoff valves' and floats to turn their water off. Does anyone have long term experience with that setup?

08/21/2016, 06:42 PM
5th not needed.. totally fine..
Its made to take the pressure..

08/22/2016, 01:20 AM
This is what I did with mine




08/22/2016, 06:41 AM
That is very similar to what I just started with a pi except i will only have two solenoids one to bypass the DI and one to open out of DI.

Buckeye Hydro
09/05/2016, 03:31 AM
Make sure that ALL wetted surfaces in contact with RO water or DI water are compatible - most are not.

09/10/2016, 02:28 PM
I also have one made using an Arduino, used 2 silinods to flush the membrane then fills the container when empty, working great for 6 months