RODI top off drain

[telamont]

Hi,
I am setting up an RODI with two reservoirs; one for RODI water and the other for the leftover water. I need help designing a system that automatically drains when the runoff reservoir gets full. I do not have enough storage space for all the runoff water I might be making but want to collect as much as possible so am setting up a 75g drum. This system will be automated with a auto shutoff for when the RODI reservoir fills. Is my only way to have the waste reservoir drain when it gets to full is to use gravity? Should I drill a hole at the top and bulkhead a 1/2" piping flowing downwards to a sink or drain? Thanks for the help.

 

[mmn]

Gravity is certainly the most reliable way, if that's an option. It's how rain barrel overflows work.

 

[tkeracer619]

Why not straight into the drain?

 

[sleepydoc]

+1
What's your actual goal? To have 20 gallons of RO waste water to use? Not to waste any water?

Most people simply run the waste line to the drain. If you have a use for the RO waste water, you dump it into a container and have a bulkhead at the top of the container with tubing running to the drain, so it would fill up the container and any excess would then go down the drain.