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Kitchen faucet connection size

How do I determine whether the connection size needed to connect new faucet to existing pipe is 3/8" or 1/2"?

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Posted 2014-01-21T15:17:27+0000  by clt0193 clt0193

Hello clt0193.  Welcome to the Community!


Pipe and fitting sizes for plumbing parts can be confusing, as the dimensions are based on the inside diameter of the pipes.  While with experience one can tell size just by looking at it, you can also estimate the size by measuring the outside, (which you can see), and estimating what the inside dimension is.  There is a significant visual difference between 3/8" and 1/2" plumbing.  Take a look at the pictures below:


Plumbing Sizes.png





This is the most common setup for a faucet connection for either a kitchen or a bathroom.  The bath faucet shown has a pair of 1/2" pipe thread inlets.  If you measure the outside, it will be around 3/4".  The supply line pictured above has a larger nut which is also 1/2" pipe thread, and a smaller nut which is a 3/8" compression thread connection.  The stop valve also has a 3/8" compression thread outlet, with an inlet designed, (in this case) for connecting to 1/2" copper pipe.  It is this inlet or stop valve that often causes the most confusion, as the plumbing in any given home can vary widely.  If you are replacing that stop valve, then you will need to know whether the pipe it attached to is silver galvanized steel, or copper.  While 1/2" is the most common, measuring the outside of the pipe will allow you to tell 3/8" Inside vs. 1/2" Inside diameter pipe.  While bath plumbing can be either size, I have never seen plumbing pipe going to a kitchen other than 1/2".  The type of pipe can vary, but the size does not seem to.  For copper pipe, the stop valve comes in either compression fitting as shown or a model that is soldered directly to the pipe.


One last thing.  Some faucets come with the supply lines integral with the faucet body, rather than the 1/2" nipple setup shown.  If yours is like that, then the ends of these supply lines that attach to the stop valve will most likely by 3/8" compression fittings, just like the smaller end of the supply line picture as shown above.

See the picture below for an example of this, often found on faucets that feed the water supply through a single center hole as shown:

Kitchen Faucet.png

I will admit that this is harder to type out in words than it is to show and explain in my store.  Your local Home Depot plumbing associate should easily be able to get you set up with what you need to complete your new faucet installation.


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Posted 2014-01-21T17:35:31+0000  by Chris_HD_CHI
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