Cut pipe behind backflow preventer?

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Magicalpig

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I have to make some changes on the hot water pipe going from my water heater into my boiler. In the interest of not having to empty the boiler, I'm wondering if I can cut the pipe somewhere behind the backflow preventer that's between the two appliances. Will the backflow preventer keep all the contents of the boiler from rushing out where I make the cut??
 

Terry

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I have to make some changes on the hot water pipe going from my water heater into my boiler. In the interest of not having to empty the boiler, I'm wondering if I can cut the pipe somewhere behind the backflow preventer that's between the two appliances. Will the backflow preventer keep all the contents of the boiler from rushing out where I make the cut??

I would not count on that. If the backflow is combined with a shutoff, maybe.
 

Magicalpig

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it's a Watts 9D-M3 and I don't have any shutoffs downstream of it. It's on a pipe that connects the boiler to my water heater's hot output. I need to add some height to this pipe because I'm changing my short water heater for a tall one.
 

Jadnashua

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The boiler heating loop and your potable water SHOULD NOT be able to cross-contaminate (i.e., boiler water should never be able to get back to the potable water). If you find that it does, it needs service NOW.
 

Magicalpig

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I understand if you can't give me a definitive answer. There's a chance I'll have to drain the boiler out anyway if I end up changing a kickspace heater to use monoflow tees, depending on how people respond to another thread of mine.

Thanks, all.
 
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