I am re-installing an undersink water filteration system. The supply line for the filter is a 1/4" flexible plastic tubing.
Also, I don't want the filteration constantly supplied with water. We should be able to turn the water supply on and off to the filteration system.
The current cold water valve and supply line is 3/8".
What sort of valves and fittings do I need for this project. I know there will be some sort of T-connector involved and there will be some kind of valve to turn the supply on/off to the filteration system.


Any help you can provide with the links to the plumbing supplies on homedepot/lowes website will be much appreciated.


Thank you.

Do have a opening un your si8ng to install a chrome water tap? If not do you have a stainless steel sink? What you want to do is doable but you will need tools and some plumbing skills, Still want to proceed? Back to you, Tom

What type of piping do you have, copper of CPVC?

Does piping come through the back of the cabinet or the floor?
Do you have enough room between the existing stop valve and the back or the floor to install a tee fitting?

The supply line for the filter is a 1/4" flexible plastic tubing
Is that 1/4" inside diameter or outside diameter? A 1/4" inside diameter should be 3/8" outside diameter.

They are metal pipes, but not copper coming out of the floor.
Yes I have enough room all around.
1/4" is outside diameter of the tubing

If pipes are metal but not copper they must be galvanized iron pipes.
Check out this coupling at Home Depot.
Watts 3/8 in. x 1/4 in. Brass Female Compression x Compression Adapter-LF A157 at The Home Depot (http://www.homedepot.com/p/Watts-3-8-in-x-1-4-in-Brass-Female-Compression-x-Compression-Adapter-LF-A157/202254863)

If plastic tubing fits this adapter;

Remove existing stop valve and install galvanized tee. Install short nipple in each out port. Install a 1/4 turn FIP (female iron pipe) to 3/8" compression stop valve on each nipple. Reconnect faucet to one valve. Put adapter on the second valve. Connect plastic tubing to adapter. You will need a brass sleeve inside plastic tubing. You may have to buy a 1/4 coupling to get that sleeve.

Probably this is exactly the part I was looking for. I am still not sure about the process you've described of adding nipples. But I will defintiely get this part and give it a try. I will let you all know.

You guys are great!

Thank you.


If pipes are metal but not copper they must be galvanized iron pipes.
Check out this coupling at Home Depot.
Watts 3/8 in. x 1/4 in. Brass Female Compression x Compression Adapter-LF A157 at The Home Depot (http://www.homedepot.com/p/Watts-3-8-in-x-1-4-in-Brass-Female-Compression-x-Compression-Adapter-LF-A157/202254863)

If plastic tubing fits this adapter;

Remove existing stop valve and install galvanized tee. Install short nipple in each out port. Install a 1/4 turn FIP (female iron pipe) to 3/8" compression stop valve on each nipple. Reconnect faucet to one valve. Put adapter on the second valve. Connect plastic tubing to adapter. You will need a brass sleeve inside plastic tubing. You may have to buy a 1/4 coupling to get that sleeve.