3/4" Copper Supply Pipes under Sink?

[Troodon]

I've been investigating our bathroom sink, to put a vanity where now there is an old pedestal sink. The supply pipes coming out of the wall seem to be about 7/8" in outer diameter. Does that mean these are 3/4" copper pipes? The hot water valve sticks out of the wall about 5 inches, and the cold about 3. I wanted to cut the pipe of the hot one and replace the valve, but am finding only 3/8 and 1/2 inch inlet valves. Is it unusual to have such large-diameter supply pipes?

Cold water:

Hot water:

We're thinking of putting in an IKEA vanity, hence the desire to provide clearance closer to the wall. The house was built in 1939, Bay Area, California.

Thank you.

 

[Reach4]

1/2 inch galvanized is 0.840 inch OD. You may have that.

See if the pipe is attracted to a magnet.

 

[Sponsor]

 

[Jadnashua]

You'll know if it's attracted to a magnet, but it does look like it's a galvanized pipe nipple. While they come in various lengths, often, the plumber uses the one(s) he has on his truck rather than potentially getting the ideal size. But, galvanized piping is a lousy choice for potable water...it will always, eventually, rust. If all of your piping is galvanized, plan for a future repipe. If the pipe in the wall is copper, then, it would be best to replace that with a brass nipple which should last your lifetime without issues. Hot water pipes tend to rust first.

 

[Michael Young]

I've been investigating our bathroom sink, to put a vanity where now there is an old pedestal sink. The supply pipes coming out of the wall seem to be about 7/8" in outer diameter. Does that mean these are 3/4" copper pipes? The hot water valve sticks out of the wall about 5 inches, and the cold about 3. I wanted to cut the pipe of the hot one and replace the valve, but am finding only 3/8 and 1/2 inch inlet valves. Is it unusual to have such large-diameter supply pipes?

Cold water:
View attachment 47710

Hot water:
View attachment 47711

We're thinking of putting in an IKEA vanity, hence the desire to provide clearance closer to the wall. The house was built in 1939, Bay Area, California.

Thank you.

Do yourself a giant favor and while you're doing your project, get that old galvanized shit cut out and into the garbage.

YOU DO NOT HAVE TO CUT THE WALL.
1: go underneath and you'll see the two drops
2: cut them loose and use a large pipe wrench to loosen up the threads
3: go upstairs and use your pipe wrench to loosen those threads
(loose your threads until you can unscrew the pipe by hand)
4: go underneath and unscrew the drop
5: go upstairs and pull the pipe towards you and finish unscrewing it. (this is why you want it loose)
(now you have two holes)
6: shove a piece of pex from the bottom up on both the hot and cold side
7: REACH INTO THE HOLE UNDER YOUR CABINET WITH LONG NEEDLE NOSE PLIERS. Grab hold of the pipe, crush the end. hold on tight and wiggle it through the hole.
(now you have pex pipe with a destroyed end)
8: Pull the pipe out so you have a sweep (not a kink) inside the wall.
9: cut your crush end piece
10: crimp on an ell fitting to the pieces hanging out of the wall
11: crimp on an 8" piece of PEX (this is what you'll see under the cabinet)
12: push the pipe down so the ell is inside the wall

 

[Troodon]

Yup.

 

[Troodon]

Thanks for the advice and step-by-step instructions. I spent a while squatting and shuffling around under my house yesterday, trying to look at the plumbing. Gosh I have to buy kneepads and a plastic suit. Anyway, it's a mix of galvanized and copper, the copper maybe due to a kitchen remodel and new water heater being installed in the last 8 or 9 years. But over by the bathroom it looks all galvanized.

Some of what I found (though not by the bathroom):

I'm researching PEX-to-galvanized connections, lots of it leading to threads on this forum. I'd actually been watching YouTube videos on how to solder copper and use dielectric fittings, thinking I'd have to do (learn) that, but the PEX route sure seems easier.

 

[Terry]

You have pictures of 6" long brass nipples being used as the connection between copper and galvanized. That's how I do that too.
They make a true dielectric union, but they're worthless.

 

[Troodon]

Worthless because of corrosion?

The vanity project's on hold. So now that I'm thinking about replacing the sink drops with PEX, I'm also wondering about what's beyond the drops. I mean, if that project went well, and I felt OK both removing galvanized pipe and installing the PEX, then might I go on replacing some of the other galvanized pipes, too? Obviously, if I did so, I'd want to be doing it according to best practice / code. I wouldn't want someone going under the house in 15 years and rolling their eyes at what some hack did to his plumbing system.

 

[Jadnashua]

Pex has its good and bad points.
Good:
- flexible so you can bend it verses use a lot of fittings
- less friction because of fewer fittings and smoother
- usually faster to install
- usually cheaper than say copper
- won't be damaged by freezing, but that's not true of fittings which can split if frozen
Bad:
- the ID is smaller than the equivalent sized copper (the OD is the same, the pex tubing wall is LOTS thicker)
- must not be exposed to UV as that will degrade it
- mice tend to chew on it
- it 'looks' sloppy and if you're a neat freak, you won't like it (doesn't affect the utility of the stuff at all, though)
- the fittings going INSIDE of the tubing, add more restriction...if you choose a type-A pex and expansion fittings, the restriction is less. The expansion tool is more expensive than a crimp tool, but then, you have more room for installation error if you don't crimp them right or your tool is uncalibrated. The crimp rings aren't free, but they're not particularly expensive. You MIGHT be able to cut off a crimp ring without damaging th etubing, but if you wanted to change an expansion fitting, you have to cut the tubing and fitting off, then, if you're careful, you can slit the tubing left on the fitting and reuse it if it's not scored up.

I'm sure I've missed some in each category. Because of the ID differences, you may need to bump the supply line size up for a high volume device, or at least for the main trunk, then branch off to individual points of use.

 

[Treeman]

That galvanized Tee looks to be growing a pinhole leak as we speak!

 

[Troodon]

Sorry for the random development of this thread, but I'm learning as I go here so there's not really an educated master plan. I still have the pipe thing on hold, mostly because it's more complicated than I feel I can do now. I decided to try putting in a plumbing access door behind the shower. I wanted to do this anyway, but since the access would be through a closet, I also thought it would be a good way to learn how to cut our walls, before possibly doing that for the sink.

So I cut through the plaster and lath today using an oscillating tool, and made a preliminary 6x6 hole so I could peer in and see what size access door would be good (we have irregularly spaced studs). Immediately beyond the lath is the back side of a 2x4, which is nailed between studs and to which are "clamped" the tub pipes, hot and cold. In the first picture you can see the nails, which were bent down after being used to fix the pipe holder/clamp things to the 2x4 (sorry for the wrong terms!). The second picture is peeping over the 2x4, showing the hot water side. The third picture is similar, and it really looks like they never wanted anyone to be able to change these pipes or even look at them until the end of time.

My question is, do I just leave this support 2x4 here, even though it blocks access to the pipes, and proceed with an access panel (I'm thinking either 12x12 or 14x14)? Should the panel opening be centered on the horizontal hot/cold pipe? Or a bit lower or higher? Any other thoughts? We would like eventually to change these pipes and the tub fixtures, which together produce a lot of loud whining, some water hammer, and don't work that well. But I'm not sure what I'm looking at here in my wall!

And thank you for all the responses, which have led to all kinds of research on my part.

 

[Jadnashua]

Well, the outside of the pipes look good, but you won't know the state of the insides unless you take one apart and check.

Galvanized piping can last awhile, but almost always, given enough time, it will rust, usually from the inside out. The ID may be quite small by now, restricting the flow. It's often worse on the hot water side.

Your tub/shower valve would need to be changed if you start modifying much, as it would then require updating the parts you touch to current codes (which, in the case of a shower, would need a valve with anti-scald technology. You are allowed to repair, but cannot replace unless it meets current code.

The blocking is there to hold the pipes rigid so when you turn the water on/off, the handles and valve body don't move around. Plus, flex can be tough on joints. You will want some behind the valve, and adding it from the back side would be tough, but not impossible if you got creative.

 

[Troodon]

Hey thanks, and for your PEX breakdown, too. What do you mean "adding it from the back side"? Isn't this already behind the valve and fixtures? But you must mean something else.

 

[Jadnashua]

Adding a clamp to the pipe on the other side of the blocking (i.e., the back side)...

 

[Bcarlson78248]

The galvanized drain pipes in my 2nd floor bathroom are just like that - embedded in the cement they used under the tile. They are impossible to remove without a complete demolition of the floor.

Now for the bad (or a little worse) news about the galvanized drain pipes. Since they are horizontal, water stays in the bottom after you drain the tub or sink, and its always a humid environment. After a while the iron forms deposits on the bottom that look like stalagmites in caves. It creates a very rough bottom surface that collects anything draining through the pipe, like hair, skin particles, excess shampoo, etc. It does not usually plug the pipe, but we have found that it helps a lot to flush the drain with a diluted bleach solution about once a month to ensure that it will not begin to smell bad. It is not like a strong sewer smell, but more like just a funky. mildew-like smell that is mildly unpleasant.

Bruce

 

[Jadnashua]

IF drain pipes have proper slope, there should not be standing water in them (except in the p-trap). On galvanized piping, though, as it starts to corrode, the rough areas can leave pockets that can stay wet. If it's past the p-trap, you should not notice, but anything above the p-trap, you will. The long-term goal should be to excise any galvanized piping in the place.