Expert: Dana Bostick - 7/9/2009

Question
QUESTION: I need to have a water valve replaced.  The home depot expert says I can desolder to remove the old valve and solder in the new valve.

When desolder and solder, do I have to aim the propane torch all around the pipe or I can just aim it at one area and let heat conductivity take over (it's right below the wood joist).

Also, I saw some where there is like 3 sizes of 3/4" pipe, j, k, and m.  Does a standard water valve fit in all 3 sizes and can I tell without measuring?

ANSWER: Hello David,
Yes, copper pipe comes in three grades; M, L and K. The difference is wall thickness, not outside diameter so the valve will fit on any grade. M is light gauge, L is heavier and K is "industrial, seldom seen in residential work.

De-soldiering a valve, under the house in tight quarters, close to combustibles is difficult at best.  Not something that a novice should attempt. The tip off that you are not very experienced in doing this work was asking if you needed to mover the torch around. (yes, you do)
It gets more complicated by having any water in the line and the fact that you will fry the new valve if you don't do it correctly and over heat it. The valve should be taken apart to prevent damage if you can. Ball type valves are NOT easy to disassemble, gate valves are not as hard.

My recommendation is to have an experienced plumber do this.

Like Kenny Rogers once said "Ya gotta know when to hold em and when to fold em".
Good Luck,
Dana

---------- FOLLOW-UP ----------

QUESTION: Thanks for the additional information.  Let me back up then.

The reason I asked about replacing the valve is because the current valve (not a ball valve, it's about 30 years old) is leaking some water and very corroded at the stem.

Since you say it should be disassembled, then should I just replace the parts?  Or are parts even harder to get if they're different among manufacturers.

WOuld photos help you answer the question - I have 2?


Answer
Hello David,
So what you have is probably called a gate valve.  I think it would be almost impossible to find parts for a 30 year old valve.  It should be replaced.  With the corrosion, the stem could actually break off or the gate part become jammed in its ways and not be able to be opened again.

Given the location, I still maintain that this is something that a pro should do. This is not the place to learn the trade.  Failure could leave you with no water at all until someone could get there to fix it.
Best,
Dana