Do i need a check valve with Auto shutoff valve?

[sayn3ver]

I just bought an RO/DI unit with an auto shut off valve. I know i need a l float valve inorder to use it with my brute trashcan holding tank. DO i need a check valve as well? if so, where is it installed?

[bertoni]

I don't see any need for a check valve in that type of setup. I never used one.

[jdieck]

Originally posted by sayn3ver
I just bought an RO/DI unit with an auto shut off valve. I know i need a l float valve inorder to use it with my brute trashcan holding tank. DO i need a check valve as well? if so, where is it installed?

Yes a check valve (1 lb) is required in the pure product line between the membrane output and the ASO valve. The ASOV closes the input water when the pressure in the output water increases due to the closing of the float valve. Without the check valve the pressure in he product line will drop again as the water backflows into the membrane and out the waste line thus opening the ASOV initiating and ON/Off continuous cycle.

Check your system, if it came with the ASOV installed most probably the check valve is there, some times is installed in the membrane housing fitting of the product outlet line so it might not be very obvious.
These diagrams may help:
In the first case you only have the check valve on the product line as it is a dedicated single ouput system.
In the second diagram you need a second check valve if you use the system also for drinking water. The second check valve is optional and is there to prevent the stored water in the pressurized tank to be drained out to the aquarium reservoir or sump when collecting water for the aquarium so providing some stored water for drinking at the same time aquarium water is being produced.