Why doesn't this 3/8" COMP tee have a washer in it? And should you use thread tape?

[ngmtl]

I purchased this 3/8" COMP Dual Outlet Tee:
https://www.lowes.com/pd/Keeney-Lead-Free-Add-A-Tee-Adapter-3-8-in-x-3-8-in-x-3-8-in/1000276665

Questions:

1. Why doesn't the female connector on the tee have a washer in it?
2. Since there is no washer, do I need to use thread tape to make a seal or will that be counterproductive?

Normally (Single Faucet):

Faucet
|| 1/2" FIP Male
|| 1/2" FIP Female
|
| Supply Line
|
|| 3/8" Female COMP (has a washer in it - don't use thread tape)
|| 3/8" Male COMP
Shutoff

With Tee (For Dual Faucets)
Note: Some codes require a separate shutoff for each sink. But that's beside the question here.

Faucet x 2
|| 1/2" FIP Male x 2
|| 1/2" FIP Female x 2
|
| Supply Line x 2
|
|| 3/8" Female COMP (has a washer in it - don't use thread tape) x 2
|| 3/8" Male COMP x 2
T Dual Outlet T
|| 3/8" Female COMP (no washer! - does it need thread tape?)
|| 3/8" Male COMP
Shutoff

 

[Terry]

No tape is need on those. Tape does nothing for those, but it can cause a leak by a strand not allowing full contact where the surfaces meet. You can always tell a handyman install when you see the tape. Plumbers don't use tape there.

A braided stainless supply line that is 1/2" FIP x 3/8" comp has seals on both ends. Nothing more is needed.

 

[Sponsor]

 

[hj]

the female connection is a metal to metal surface.

 

[ngmtl]

Thanks!, I also confirmed with Keeny today that their compression tee, despite lacking a washer, is supposed to form a compression seal, metal to metal without thread tape. And to be clear, they also agree that thread tape is counterproductive here.