5 stage generic RO/DI unit - valve and drain question

[Mr31415]

I used to be in the hobby a decade ago, and am now starting back up. So my knowledge is slightly rusty. I got a generic 5 stage RO/DI unit and hooked it up. It works - but I have two questions.

1. What is the purpose of the blue on/off valve at the outflow of the DI resin canister?
2. I initially had my RO/DI unit higher than the wastewater drain outlet. When I turned off the tap to the main water supply to the unit, the waste water kept on draining via siphon - I could see the cylinders draining one by one. Why would it make a siphon? Is the purpose of the valve in question 1 above to prevent air from enabling the siphon when closing the water supply?

 

[griss]

Turning off the valve on the output of the product water is how you shut off the system when you’re done producing water, not turning it off at the water source. When you close the blue valve, it triggers the Shutoff Valve (little white box behind the RO housing) then shuts the system down and should prevent the siphoning. By turning the water off at the tap, you’re removing the pressure that would trigger the shutoff valve and turn the system off without siphoning.

 

[griss]

Let me know if that works. FWIW, if your shutoff valve goes bad, you'll still have siphoning.

 

[Mr31415]

I will try it - thanks for your help!

 

[Mr31415]

It worked, thanks again.

 

[griss]

Good deal, glad that remedied it.