Delta Tub/Shower Rough Valve - What is This Part?

[mnocket]

Getting ready to replace my old tub/shower valve with a Delta R10000 rough-in valve body. This part (pictured) came in the box and is not mentioned in the instructions and I can't see any use for it. Anyone know what it's for?

 

[Marlinman]

It is a test plug.

Pressure Test Plug - Hot / Cold RP46079 | Delta Faucet

Pressure Test Plug - Hot / Cold

www.deltafaucet.com

 

[Sponsor]

 

[Tuttles Revenge]

Its function is to prevent hot and cold from mixing in the valve and being sent to other fixtures. If you install the rough in valve now and don't have the cartridge to install, you would install that plug until you install the cartridge.

 

[LLigetfa]

Its function is to prevent hot and cold from mixing in the valve and being sent to other fixtures.

Winner winner, chicken dinner.
The test cap alone does not prevent crossover.