Soldering copper pipes - basic question

[Max]

Hi Folks,

I am thinking about replacing our water softener and doing so will require me to do some replumbing. I know that you cannot solder copper pipe that has water in it but I am wondering EXACTLY what that means. If I have a pipe that is 24" long with a shutoff valve in it 6" from one end, that means that I will have 18" of empty pipe and 6" of full pipe (see half-assed drawing below). If I want to solder onto the long, empty piece of pipe, will that work or will the fact that there is water in the pipe, albeit 18" away, stop me from getting the pipe hot enough?

I'll see if I can do a little ascii drawing:

A==================VVV======B

"=" represents the copper pipe.
A is the end I want to solder.
VVV is the closed shutoff valve.
B is the source (pipe from presure tank)

The pipe between A and VVV is empty.
The pipe between VVV and B contains water.

One other question that assumes I CAN solder this pipe. What is the minimum distance between A and VVV that would still allow me to solder the joint cleanly?

Cheers, Max

[LazyPup]

You cannot solder a piece of copper that has water in it because the water absorbs the heat until all the water has boiled away. To complicate it even more, if the point you are attempting to solder is closed the water in the pipe boils and the resulting steam continually pushes the solder out of the joint resulting in a leak.

However, Once the water is shut off and drained out of the pipe it is no problem. In fact, with a little practice, once a valve is closed and if the valve seals good, you should be able to solder a new piece of pipe onto the downstream end of that valve.

From your drawing I am assuming the VVV is indicating the valve and A is the point where you need to solder, probably where it attaches to the water softener. I would consider installing a union at the midway point between A and VVV. You could then make the solder joints with the pipe open to atmosphere in the event you have any residual water that might make steam, and once you have all the solder joints made you could close the union mechanically. (Not to mention that the code requires unions on the water softener lines anyway so you kill two birds with one stone.)

[Max]

Thanks for the reply LazyPup. It sounds like I should be all set and don't need to drain the whole system because I am soldering empty pipe. I think I understood that correctly.

I am going to try and show what my current setup is with this diagram, it's a 3-valve bypass setup:

                    |
                    |
                    +====+
                    |    |
                    V    |
                    |    |
I============V======+================MAIN
                         |
O=====SF=====V===========+

I = softener inlet
O = softener outlet
V = valve
SF = sediment filter
MAIN = pipe from pressure tank



You said "code requires unions on the water softener lines" and I don't really know what the means. I don't see any unions in my setup, can you explain their intended purpose i.e. why the code states you need to have them? Stranger still, the sediment filter is on the softener outlet. I looked through an earlier thread re: sediment filter before / after the pressure tank so you can imagine how confused I am when mine is after everything. In fact, I don't even have a sediment filter inline if the softener is bypassed e.g. for servicing. I don't particularly like the setup and I am thinking of reworking it all so that the sediment fileter is before the softener instead.

[LazyPup]

The location of the sediment filter would depend upon what the intended purpose of the sediment filter is. If it is intended to prevent silt, sand or other sediments from the well from getting into the water softener medium, then it should be on the main on the input side of the softener, on the other hand, they could be using the sediment filter to insure that no particulate matter from the water softener filtering medium is getting into the potable water supply. In that case it should be on the discharge side of the water softener vessel.

The codes require water heaters, water softener vessels, reverse osmosis machines, pressure tanks and similar devices should have unions on both the inlet and discharge lines to permit removing the vessels for servicing.

Personally when i hook up systems like this I prefer to add a bit of overkill. Gate valves are very cheap, typically about $5 each, so If i can toss in a couple extra valves that will later simplyfy servicing a unit that is the way i prefer to do it.

By example, I would put a gate valve immediately ahead of the sediment filter and a second valve directly after it. In that manner you can close both valves to isolate the sediment filter so it can easily be opened for cleaning without the necessity to drain the system.

[Max]

Being able to isolate every component sounds like good advice and something I will think about if / when I replumb this thing.

Thanks for the tips.