Hello. I have a closed ball valve in an old building that is live on one side (i.e., pressurized, water) and, on the other side, is just an open female sweat fitting. I would like to add a shutoff to the open side. May I just sweat the desired fittings plus shutoff to the open side without shutting off and draining the system? Thanks for any input.

yes you may.. it is done all the time

Just don't burn up the ball plastic parts. Solder and quickly cool with spray bottle of water.

Thanks for the replies, guys. Two quick follow-up questions, please:

1. Will it take longer to hea the side I'm soldering by virtue of the adjacent, nearby water (i.e., heat sink)?

2. Is there any risk of the water boiling and the pipe bursting on the live side?

Thanks.

1) depends on the type torch you are using. a properly sized tip burning mapp gas would not take any longer but a small tip bernzomatic homeowner variety torch will take a few seconds longer.
2) the water in the pipe will make it impossible to heat the joint to the approx 450 deg needed to get it apart.

just ask any plumber who has tried to solder a joint with a little water just laying in the pipe.

You are trying to add a shutoff after the ball valve which is a shutoff. Is this because the ball valve is not working right or you just want two shutoffs in series as some kind of insurance in case one breaks?

I want to make sure you are not referring to a plug or a cap when you said "shutoff" because if that is the case it will be difficult to solder that in a closed space with nowhere for the expanded air to escape.

You're right, my use of "shutoff" in the "after" context was weird. Apologies, I should have said "boiler valve". I just want a place to hook up a garden hose. It's inside, but it's in a work room. E.g., I was recently mixing some hot mud there and nearby water would have been handy.

Thanks for all the help everyone. I took care of this today and all is well.



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