RODI accessories questions

I have a 5 stage RODI unit, and I am changing the filters this week. I am converting it to a dual DI system by getting rid of one of the carbon filters.

My problem is that the housings won't fit to the metal bracket correctly with this arrangement. This is because they make the screws in a rectangle! Stupid stupid. Does home depot or lowes sell metal brackets like this?

Next, I want to buy some fittings so that I can include a DI bypass, and RO sample port, and an easy way to drain the system when I am cleaning it/changing filters. Does anyone have any diagrams that can help me do this?

What are the importance of check valves? Where is it important to include them?

How can I incorporate a way to drain the entire system?

 

Any of the RO vendors will sell a new top bracket for a reasonable price, you might order one at the same time you order the new filters. The brackets I am used to seeing have multiple holes so you can rotate the canisters freely. You won't find a bracket at the hardware store.
For a DI bypass/sample port you need a 1/4" John Guest style tee, a couple inches of 1/4" tubing and a 1/4" ball valve. Install it between the RO membrane and the DI canister.
A check valve is used for a couple different purposes. For one they are used if you have a drinking water kit with a pressure tank where they isolate the RO only pressure tank from the DI filter so you keep seperated. You do not want to make DI water with RO wate rstored in a pressure tank since they are prone to TDS Creep and will exhaust DI resin much quicker than making DI straight from the RO membrane. Pressure tanks tend to make a system cycle on and off frequently to refill the pressure tank and every time you start and stop a RO membrane you get TDS creep which eventually concentrates or builds up in the pressure tank. Fine for drinking but not so good for DI resin.
Another use for a check valve is to make a autoshutoff valve (ASOV) operate better, often when using a float valve in a ATO container the ASOV does not shut off drip tight and the waste keeps running. A check valve will often cure this.

A drain really isn't necessary. As long as you relieve the pressure on the RO/DI system the housings should unscrew easily and can be dumped out and cleaned at the recommended 6 month intervals. I am not sure whay you want to drain them?

 

How do I relieve this pressure?

 

If you have a RO/DI without an autoshutoff valve just turn the tap water feed off and leave the RO/DI outlet line open.

If you have an autoshutoff valve hooked to a float valve lower the float to relieve the outlet pressure.

If you have an ASOV hooked to a solenoid valve and float switches, activate the fill or lower switch again to relieve the pressure.

If you have a drinking water pressure tank either bleed the pressure off the tank by opening the faucet and letting it drain or close the ball valve on the top of the pressure tank and disconnect the line to the tank to relieve the pressure.