Thats a 5 psi relief valve? When you shut down you just open it and prevent pull back, vacuum into the boiler? That is pretty economical.BlackStrap wrote: ↑Sat Dec 19, 2020 1:31 pm Anytime the vapor path is not open to the atmosphere it is then a closed system. Period!
adding a thumper would make a system "closed"
Adding a relief valve is HIGHLY recommended.
This is mine. drilled and tapped into a 2" tricover "blank" cover"
It's placed between the 1st boiler and 2nd boiler "thumper" it is 5psi and cost $7.00 us dollars on Amazon.
Would be easy to test in real world situation as well to ensure it works. Inline ball or gate valve after that point to just to test the relief valve.
Put a steam whistle on it and it will wake anyone having a nap!