How far away must water be for me to solder?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by lithnights, Mar 21, 2006.

  1. lithnights

    lithnights New Member

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    I know by reading and by experience that there can be NO water near the join when trying to solder.

    But that leads me to wonder how close water CAN be to the join? e.g. if I have 1/2" copper running horizontally and there is a T installed which copper piece running up vertically from the T.... If I want to solder a cap onto that vertical copper (or unsolder an existing cap), how far away must the cap be from the 1/2" horizontal pipe that may have water? I would think the heat would make the standing water boil and thus jump up to the join area, thus making soldering impossible? Or is it fine as long as no water is TOUCHING the join area?

    Hopefully my attachment (2nd grade drawing using Paint) helps explain what I mean.

    I would try to drain all water but that's not always possible in this type of situation.

    Thanks,

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    Last edited: Mar 21, 2006
  2. hj

    hj Moderator & Master Plumber Staff Member

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    water

    In your drawing the water would be far enough away to permit the soldering, but the air trapped between the cap and water would be expanding as it got hot and would probably either blow the cap off or blow though the solder creating a pinhole leak.
  3. lithnights

    lithnights New Member

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    Location:
    PA

    OK.. assume the water level in that 1/2" horizontal pipe is only half high.. in other words only half the pipe is filled b/c I was able to drain much of it.

    Would the air still be an issue? I would think not because there would now be an air passage in the horizontal pipe. Agree?
  4. Cass

    Cass Plumber

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    The air will expand and cause a problem no matter how low the water is.

    There must be an open path to the atmosphere some where in the line in order to not build pressure.

    You could solder a valve on instead of a cap then close the valve when you were done or solder on a male adapter and screw on a brass cap when you are done.
  5. prashster

    prashster New Member

    Messages:
    941
    not a pro

    I respectfully disagree.

    1/2 water and 1/2 air in the pipe is fine.

    A little water in the line away from the soldered joint is actually preferable. Water is an excellent heat sink (better than air) in that it requires more energy to heat than air.

    Further, as long as there are no sensitive joints/valves within 4-5 feet, you don't even need the opposite end to be open to the air. The copper and water will conduct the heat through the pipe sufficiently. Test this yourself by wrapping a wet rag around the pipe 5 feet away from the joint and soldering the cap. If the rag starts to sizzle and steam, it is getting hot. (Actually, the presence of a wet rag is also a good thing, bkz it'll conduct heat away from the pipe better than the atmosphere will.)

    Caveat: I'm an engineer, but not a plumber. The only emprical evidence I have for this 'theory' is my own experience. I've soldered a closed cap onto a sealed line with 10 feet in between the cap and a ball valve. The copper pipe more than 5-6 feet away from the cap was cold to the touch (which means it had NO hot air in it).
    Last edited: Mar 21, 2006
  6. Cass

    Cass Plumber

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    With all due respect you are an engineer. :)

    It is possible to solder a closed system but you may end up with a problem and it may not show up for a while, due to expanding / contracting air.

    Please tell me how you solder a cap on a closed copper line and not heat any of the air inside the line?
  7. prashster

    prashster New Member

    Messages:
    941
    The air inside the line heats, yes. But the copper heats too. Copper is an excellent conductor of energy and heat. The pipe itself sinks the heat to the atmosphere.

    Of course, it's not as good as air, so if you only have a short run btn the solder joint and another sensitive part like a valve, then you gotta have air movement - or a wet rag heat sink. But, if you have a long enough run of just copper - or even copper with a little water in it, then the air will transfer its energy very efficiently to the copper and to the outside air without making its way too far down the pipe.

    If this were not true, then copper pipes would take a long time to get hot to the touch, and take a long time to cool to the touch - neither of which is the case. I've said this time and again, but wrapping the pipe with a wet rag a distance away is the best way to sink heat away from a pipe and to protect sensitive parts 'upstream'. Lithnight's water-in-the-pipe situation is the same thing. The water takes the heat instead of the air with far less expansion than air.

    Anyway, it seems like an inexpensive test. Try it. Again, you'll know if you didn't hurt anything else if that tee stays cool, and if the upstream pipe stays cool.
    Last edited: Mar 21, 2006
  8. Cass

    Cass Plumber

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    Location:
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    You need to get real world experience instead of theory.

    After all you are an engineer. :)

    Like I said it is possible but can be very difficult to near impossible and time consuming if there is a leak. Not worth the effort and time in my NSHO.
  9. lithnights

    lithnights New Member

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    I'll give it a shot. I actually read in a book that such stub ups were often installed and capped in an effort to have air in the system which would reduce noise from the pipes. Sound about right? I think it's in one of my Black and Decker Plumbing how-to books.

    Another reason I asked was (cap aside), if I was to try to install a shut off valve (replace the cap with a ball valve in my drawing) close to water, would I have problems with soldering...? That is likely what I will be doing.

    Thus, is there a distance in inches or volume of pipe that water needs to be away from the join?
  10. prashster

    prashster New Member

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    941
    Cass,
    I'm not a plumber, but I have soldered quite a bit, and I've done a few caps in my day in the manner I've described. Most have been pretty good ;)

    As always, I respectfully defer to your experience, but I gotta say my response is from experience too - not theory (though the theory seems to reinforce my experience).
  11. jimbo

    jimbo Plumber

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    San Diego
    Well, it all boils down to the distance. If that riser was 3 or 4 inches, you might get it to solder before the air in the riser heats up enough to cause problems. If it is closer, the water might even boil.

    As a practical matter, it seems like there must be an open end to the horizontal pipe. Obviously it is not pressurized, so if this is just a residential situation, we would always open a tap somewhere so that line would not be a closed line.

    Think about a pipe freeze machine or a JetSweat. They are blocking water only 6 to 8 inches away.
  12. prashster

    prashster New Member

    Messages:
    941
    If you solder a shut-off valve, you'll be ok. Just make sure the valve is in the open position, bkz the heat can damage the gasketing device easier than it can a copper cap. It doesn't matter how close the thing is to the water. As long as it's not touching or flowing through the soldered joint. I'd be more worried about harming the tee joint on the stub. To that end, wrap it with wet rag (I know, I'm a broken record).

    IMHO, I'd put a valve instead of a cap anyway. The reason to stub like that is bkz you're eventually gonna put something there. When that day comes, you gotta drain the main line to solder the extension. With a valve, you don't have to do that. Put in a threaded valve so your 'extension' can be screwed in and any downstream soldering will be a safe distance from the valve.

    As for the stub acting as a hammer arrester. That's not a great solution. The 'chamber' will only arrest the water pressure until it fills with water itself. This can happen in a few days. Once it becomes logged with h2o, you have to drain the system and 'recharge' it. Bad. The only thing a stub will do for you is to provide a convenient place to put a specially designed arrester in place. That thing is a shock absorber that doesn't get logged with water and keeps working.
  13. lithnights

    lithnights New Member

    Messages:
    143
    Location:
    PA

    I do agree about using the valve instead of the cap. I guess I was just curious about soldering close to water in general. Regarding "As long as it's not touching or flowing through the soldered joint. " what I noticed in my last soldering job was that a bit of water close by got heated, boiled up and got onto my soldering area. Pain in the.... I couldn't solder until it was all dried up... even though the water wasn't in the joint when soldering began.

    I know nothing about arresters but what you say makes sense.

    thanks,
  14. prashster

    prashster New Member

    Messages:
    941
    You can buy arrestors from HD for $11. They look on the outside almost like a short stretch of pipe with a cap on the end. But the inside is different.

    If the water is 80-90% drained from the horizontal part of the pipe, you can use white bread or plumbers bread to stop the flow of water completely for a short amount of time - enough to get the valve on. The water pressure will blow that stuff into smitherenes later. Just don't use rye bread like I did my first go-round, unless you love clogged sink aerators.
  15. lithnights

    lithnights New Member

    Messages:
    143
    Location:
    PA

    Right on about the bread, that's exactly what I ended up using. Didn't use rye but it still clogged the heck out of my one sink aerator. Then again the thing probably hadn't been cleaned out in years.
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