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How to sweat a press connection?

arbour Member Posts: 2
Hi - new here, so please be gentle...

I'm a homeowner, and I'm adding a zone to my heating system for my basement. In searching out the parts that I need, I found the right model zone valve online, and ordered it it - the photo showed a 3/4" sweat connection, but when it arrived, both the inlet and output are unions with press connections - I looked at the product description and sure enough, it says "press" - though I didn't know what that meant at the time I ordered it. Rookie mistake...

So, I got the wrong thing, and the only options I see are:
- Buy an $1,800 tool from home depot to connect two fittings
- Return the valve and scour the internet trying to find another one (and lose out on at least $30 in shipping costs)
- Buy the "Caleffi solar fitting sweat kit" (NA12259) that I think will replace the press unions, but I can't be sure because I don't know a lot about this stuff ($30 after shipping), and risk wasting my money
- Remove the rubber O-ring inside the press connection, fill the gap with solder (effectively turning it into a pre-soldered fitting) and try sweating it onto the 3/4 copper pipe.

I'm inclined to try the 4th option - has anyone ever done something like that and had success? The way I look at it, it wouldn't be any different than a pre-soldered fitting after all is said and done...

Please let me know what you think - thanks!


  • Jamie Hall
    Jamie Hall Member Posts: 21,536
    There's a fifth option: make it up a pair of shortish 3/4 copper nipples, with a sweat coupling joint on one end of each. Sweat those to your planned copper pipes. Then use the other end to connect to the press unions on the pump. Unions are always nice to have...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SWEI
    SWEI Member Posts: 7,356
    ...and a sixth: Most supply houses that sell press will lend or rent the tooling.
    delta T
  • hot_rod
    hot_rod Member Posts: 19,899
    Got a picture of the valve? If it is a Caleffi brand, I would be happy to drop a couple sweat tailpieces in the mail for you. That would be the simplest, cleanest method.

    i think the tolerance in press fittings it too lose to solder well. I have silver soldered over them on a couple occasions :)

    Many plumbing wholesalers have press tools to rent or loan out, maybe call around. Or contact a Milwaukee rep for a demo tool :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • arbour
    arbour Member Posts: 2