Valve replacement at main supply

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poorboywilly

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The handle has stripped off the main shutoff valve inside my house. I'm looking to replace it but there are a couple issues I'm considering.

First is the fact that the supply line here is copper, while most of the house is plumbed with galvanized. Currently installed is a stop and waste valve with copper sweat connections on each side, and above the valve is a sweat to MIP adapter that is connected directly to the galvanized pipe that leads to the rest of the house. I do not want to reinstall copper on galvanized like this as I wish to avoid galvanic corrosion.

Second, this valve is located in a subfloor crawlspace which requires a minute to access and it gets rather cold in the winter. Also right above this valve is a tee, one side which leads to a stop a waste valve and then an exterior hose bib. This location froze and broke over the winter, but there is an electric heat tape installed now to avoid this in the future.

First question. Initially I was going to install a dielectric union to transition from the copper to the galvanized. Now I'm thinking it would be better, both in terms of ease of installation and in reducing the chance for a leaking dielectric union in a somewhat difficult to access space, to use CPVC to transition between the metals. I'll screw (with thread seal) CPVC fittings onto a galvanized nipple on one end and a copper sweat to MIP adapter on the other end, with CPVC pipe between. Are there any disadvantages to this approach? Is CPVC okay with the electric heat tape? Any code issues that could be involved here?

Second question, what kind of valve should I put here? Should I use a CPVC valve, or should I put a brass valve on the copper end and then transition? I like ball valves due to their ease of operation, do they have any disadvantage in this application?

Any other issues I haven't thought of or explored yet? Thanks for the help!
 
A good quality brass ball valve is definitely recommended in this application.

As far as the transition goes I would go with the dielectric union. CPVC is not a material that I would ever recommend installing.
 
I think it's fair to call people's opinions of dielectric unions (at least as far as I have seen) "mixed". Lots of people claim it's a leak waiting to happen, your thoughts on this?

Also, out of curiosity, why are you down on CPVC?
 
First the dielectrics. Nearly every water heater I have serviced or replaced has utilized dielectric unions. Rarely has the source of the call been from a leaking dielectric union.

On to the CPVC. This material is prone to cracks and splits. Also if it requires repair you are forced to use a glue joint. Almost all of the glues on the market recommend a 24 hour cure time. I hate to tell my customer they have to wait 24 hours before I can even leak check my work. That said I have had to make such repairs and I am reminded of an instance about a year ago.

I was changing out angle stops in a condo that utilized CPVC. After completing the swap my helper and I went to lunch. We also went to the supply house. We killed about an hour and a half before returning to the job to turn on the water. Any plumber will tell you that this is a nerve racking moment. Water on, and no gushers. Phew, dodged a bullet there. Now on to repairing the drain below the kitchen faucet. As I completed my repair on the drain I turned the faucet on and off a few times. THE NEW STOP CAME OFF!!!! Half inch hot water line flowing full on in a hardwood kitchen owned by an older woman who never had kids (immaculate home). I quickly put my hand over the open pipe and screamed to my apprentice to shut the house down. The palm of my hand blistered form the burn in the shape of the Olympic rings.

Did I mention its prone to cracks and splits?
 
I agree as far as using a good quality brass ball valve. And in the situation you are describing, it wouldn't make a lot of sense to use CPVC to avoid a dielectric union. I just haven't run into a lot of problems with dielectric unions.

But now I gotta disagree.:D

I have been doing plumbing, mostly new installation, with some remodel and service work mixed in, for ~ 16 years. Most of the installations I have done have been with CPVC, with a decent amount of copper as well. If I were to build my own home, I would use either K copper or CPVC, period.

The two biggest problems that I see with CPVC are cheap pipe and cement, and substandard installation. No excuse for either, use Charlotte Flowgaurd Gold pipe, and IPS cements, and don't shortcut your work. Make sure your piping is straight and square, use plenty of glue on the outside of the pipe and a very small amount on the inside. Remove any burrs on the cut end of the pipe. Give the pipe a slight twist as you push it into the fitting, and wipe off the excess glue. And complete cure time is 24 hours in many cases, correct, but in coldwater situations, Noveon, the maker of the resin for the FlowGaurd Gold line, reccomends a 10 minute wait before testing to 100 PSI, and 1 minute per 10PSI beyond that. When I was doing underground plumbing for houses, the waterpipe was the last thing that was installed, and I can personally tell you that that formula is usable. 200 PSI in 20 minutes was not uncommon. The situation Reedwalker described is probably the worst imaginable strain to put on a CPVC glue joint that is not fully cured. While the pressure from the hot water is trying to pull the joint apart (hot water is "harder" on a plastic than is cold water), the joint is also twisted by the stop being turned on and off. Not at all surprising that it came apart.

Gotta run, a brewpot is calling my name. More later.

Edit: More later that I promised earlier.

Noveon had a piece of CPVC pipe with fittings that was assembled back sometime in the early '70's, I believe 1973. They pressurized to something like 1600 or 1800 PSI, and left it. It failed a few years ago, after ~25 years of extremely high pressure. Granted, this was a static pressure situation, which is quite different than the dynamic environment that waterpipe in a home is dealing with. But it does speak to the durability of this pipe over time.

Here in Florida, we have a rather severe problem with copper pipe failing due to bad water, acidic soil conditions, and lightning, depending on who you talk to. And to be honest, many of the pipe failures that I have seen with copper could possibly be attributed to poor installation. Still, I have yet to see a failure of CPVC pipe. It is entirely possible that it happens every day, as I don't do large amounts of service work, but I do think it interesting that all of the pipe failures I have dealt with have been with copper, and none with CPVC.
 
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Thanks for the thoughts! While there was a differing of opinions on CPVC (which I will file for future reference), it seems the consensus for my application is a dielectric union.

One more quick question: The copper is 3/4" and the galvanized is 1/2". Any thoughts on where to reduce (i.e. does it matter)?
 
I would reduce on the galvanized side of the dielectric union. The interior of the copper piping is smaller than the galvanized piping for the same nominal size.
 

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