I'm installing a pressure value and my union is leaking.
Is the secret to solving the leak to tighten it even harder? If so, is it OK to put a pipe wrench somewhere on it? What would be a good place?
Edit: What I assumed was a rubber seal actually looks like a cardboard ring. See picture. Or is it actually a seal that looks and feels like a piece of cardboard?
If it's not a seal, does it need a seal? If not a seal, then what's the sealing mechanism in this union?
Best Answer
The green thing in the picture is a fiber seal. It does look and feel like cardboard, that's normal. Fiber seals are hard when dry so they're easy to put in, and they expand when wet which makes a good seal. However this means they're single use: once it has been wet and expanded, it can't be reused. And if it is still wet, it'll be soggy and unusable anyway. Thankfully they're extremely cheap.
Anyway, after seeing the video, it looks like you forgot to put in the seal. So, unscrew the nut, then check the mating surfaces on the union are clean (no bits of crud from the water, leftovers of old seals, etc). This part is important because if both mating surfaces aren't flat, it won't seal. Wipe off with a dry rag, then put in the seal. There's only one place it'll fit in.
It isn't necessary to separate both parts of the union very far from each other, you can just push the nut out of the way and slip the joint in.
Then to tighten it, you just put one wrench on the top nut, and one on the bottom nut on the other side of the device. There's no place on the device to grab with a wrench, but that's fine, you'll just tighten both nuts at once.
Always be careful not to make the pipes turn, because that might bend them, crack a solder joint, or unscrew something else at the other end.
If the seal in the other nut is old, it's better to change it too.
Fiber seals are hard, so you'll feel it when it gets squeezed. At that point, give maybe 1/8th extra turn and you're done. It's supposed to feel quite firm.
Rubber joints are a lot softer, so it's difficult to feel the point when it's just right, you have to be careful not to overtighten, otherwise it'll squeeze out of the gap where it's supposed to sit.