Connecting CPVC to galvanized? CPVC or PEX?

17 Replies

I want to tackle replacing the water lines to the kitchen sink myself and have a couple of questions, how do I connect the new CPVC lines to the old galvanized lines at the point where I will be cutting out the old galvanized line? I don't see any fittings made for this purpose ( I may have missed it ) and I cannot find any answers on google.

I might end up going with PEX pipes, if so, is it the same as far as how to connect to galvanized lines goes?

you can buy compression fittings at lowe's or home deport for this purpose.

you can use them with all different pipe and tubing types, as long as the diameters match up.

My recommendation could be to use PEX, it's more resilient, and easier to install (bendy, hooray).  You can take out as little or as much galvanized line as is convenient or that makes sense to you.

The one thing I will say about PEX is that you should buy the fittings in bags of 50 online, you're get a WAY cheaper rate than buying them in any walk-in hardware store.

Thanks, I assume I would use that compression fitting if I was to connect the new pipes to the galvanized where it has been cut off, but what if I connect it to where it is threaded, I would need to use something like this? Right?

Also, if my current galvanized pipes are 3/4", do my new CVPC or PEX need to be 3/4" too or can I reduce it to 1/2"?

I noticed the link isn't working, I am trying again below:

Are you sure you want to keep the galvanized? I just replaced all the galvanized in our house with Pex and it was well worth the hassle. 

You should be able to take the transition question to your local hardware store, and they can show you exactly what you need. it will be much simpler than telling you online. 

My guess is that there will be about 4 different ways of doing what you want done.  Do the one that makes the most sense to you. 

If your planning on doing live in rehabs for a while I would buy the Pex tools now. its well worth it. 

@Nick Harrington

There are reducers that you can use.  I would recommend against using a threaded fitting, because it would mean that you could have to successfully remove whatever fitting was previously threaded ... it will be faster and less hassle (in my opinion) to cut the pipe where you want to and de-burr it, and add the compression fitting.

In all honesty, if you plan it out correctly, it won't take much effort to simply replace all the galvanized pipe in the house, starting right at the meter.  galvanized pipe rusts/crusts inward first, so you'll have poor water pressure and hard/gross water over time anyway.

Thanks, I will have to take another look at the lines and look into replacing it at the meter. If I end up not going down that route, can I reduce the diameter from current 3/4" galvanized pipes to the new 1/2" PEX or does the PEX have to be 3/4" too?

@Nick Harrington

The fitting that @Jeremy Pace  recommended will not work for connecting to a cut section of galvanized like you are asking. 

Those fittings work on practically every type of modern supply pipe, except galvanized, which requires a threaded transition. 

You must go back to a thread and use a threaded fitting.

You can likely reduce to 1/2", and me (and most here) would reccomend pex over cpvc.

Consider replacing all of the galvanized: cry once. 

I proactively replace galvanized with PEX in every single-family I buy.  

@Michael Herr

 good catch, I stand corrected.  In that case, I absolutely recommend that you remove as much of the galvanized as possible, and save yourself the future headaches.

To address your size question, I like to run 3/4" all around, and reduce to 1/2" when close to fixtures.  Because PEX fittings are inside the tubing, it cuts down your inner diameter, and I've occasionally experienced some 2nd and 3rd floor water pressure irregularities.

Every time I run into an issue with a supply pipe, some of all of it is replaced with PEX.

There are CPVC to 3/4" NPT adapters available.  I use them when connecting water heaters where the CPVC is in good shape.  They are CPVC on one side and metal on the other and cost about $4 at Lowes.  Really I see know reason you couldn't use the $0.45 all CPVC one which is what I did at my house, but I haven't on any rentals.  This is assuming the galvanized is NPT.  It may be something else.  I agree with the others and say rip all the galvanized out you can and replace with PEX if possible.  I am doing PEX on anything that has major repiping issues.

I believe there is a way to connect to iron pipe using a push fitting because it was done by a contractor of mine in a recent purchase.  I guess we will find out how long it holds up along with the iron pipes themselves.

Watch out with older Pex and newer PEX 1/2 there measurement standard changed.
I am out but make sure it is the same OD Outside diameter.  Pex switched the measurement from OD to ID or inside diameter or vice versa.  Confirm with plumbing pro.

As far as reducing the size you can reduce to each fixture but the "main " line needs to stay as large as possible. So if its 3/4 now feeding more than 2 or 3 fixtures you cant drop it to 1/2 for them. 

Ex. The cold line feeds 2 sinks and a toilet at 3/4 line but drops to 1/2 right ar each fixture you cant go back to the meter and run all 1/2 to those same fixtues. To much pressure loss if all are on. Also cpvc has a different od than pvc just a fyi.

Good rule of thumb on PEX is that you can run 2-3 fixtures off a 1/2 inch line. Meaning run 3/4 fro he main run and then branch off to the fixtures. Keep in mind as well that there are many kinds of PEX. I prefer Uponor (used to be wirsbo). Reason for the preference is that the crimp ring on Uponor spends all of its time compressing the tube to the fitting, since it has a "memory", whereas other PEX fittings only crimp the ring to the tube and that's it. Research it, and as I always say, Don't be cheap! Get a good PEX.

Also, @Michael Herr is absolutely correct. You have to go from the threaded fittings, and YES, replace it from the meter to the rest of the house. If you only replace chunks you will get junk clogging your fixtures because any work you do on the system will only cut the inner rust in the pipes loose.

Lastly, take the aerators off your sinks when you finish and run the faucets. If you run them for a few minutes without the aerators it will kick all the junk out and not clog the aerator. Spin it back on and you just saved yourself a lot of headache.

Originally posted by @Joshua D. :

Are you sure you want to keep the galvanized? I just replaced all the galvanized in our house with Pex and it was well worth the hassle. 


Good advice there - get rid of all galvanized when you are already into doing significant plumbing work. You can readily run PEX to bypass all existing galvanized, and that will modernize your plumbing and solve lots of silly problems at the same time. 

I was doing some plumbing this past weekend connecting CPVC to cast iron and the 3/4" CPVC compression fittings will fit around the 1/2" iron pipe.

I don't think the sharkbites or the white plastic compression fittings will work though just the CPVC compression fittings.

Here's a picture of it:

They are $3.92

Updated about 6 years ago

Another option is to use flex hose or a piece of garden hose to repair hard-to-reach areas of iron pipe. The iron pipe can also be cut using an oscillating multitool if it's hard to reach but only the titanium blades will last past a couple cuts.

@Nick Harrington

To make the transition properly (to Universal Plumbing Code) you have to use a dialectic union to make that transition however you will have to solder a pex or cpvc adapter into the dialectic union. However to avoid having to solder you can just get a Pex X Female Iron Pipe Adapter (Or using a Male Iron pip adapter and a galvanized coupling.) With my experience I would highly recommend avoiding using shark bite fittings at all costs because I have seen several blow apart and flood entire houses. 

As far as pex verses CPVC I would recommend pex for a couple reasons

1). Pex was designed to be very resiliant (you can freeze the pipes 2 or 3 times before it will burst and if you catch it before it does freeze that many times you can heat up the pipe and it will return to it's original form.

2). if you use too much glue for the CPVC it will actually keep welding the plastic and can get too thin to the point of burst pipes. (This happened to a hotel near me where the builder used too much glue on almost all the fittings and now they are ripping out all the cpvc pipes in the whole hotel.)

3). Pex is much easier and quicker to run.

This has just been from my experience as a plumber. Hopefully it helps and will save you some head ache in the future.

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