How can I fix this leaking connection in the heating system?

Question

In our heating system we have this distributor component from which the pipes are going to the individual radiators.

The connection on the right between the shut-off valve and the brass distributor is leaking, here is a close-up showing the leak.

The question: can or should I try to fix this leak without taking the connection apart, just by trying to tighten the nuts? The problem is that I don't really understand how this fitting works, whether it's a compression fitting or something else, or even which direction I should be tightening the nuts.
The leak seems to be on the left side of the connection where the brass nut is. Can I try to tighten it, and should I turn it right? Or if I tried to tighten it, then it would twist the whole shut-off valve and copper pipe on the right, so it cannot be tightened without taking the connection apart?
(The other challenge is that this is behind a brick wall, and there is very little place to maneuver, and I'm afraid that if I turn a nut in the wrong way (or try to take the whole connection apart), then I'll cause a bigger problem that I cannot fix without having to demolish some of the wall in front of this.)

Any advice is appreciated!

Answer 1

Right way to do it is to cut water off and dissasemble connection then replace sealings/broken parts.

You can try to tighten and hope to last till spring but i do not bet on that.

Be prepared that any move can break connection and replacement will be needed. Noone can say what condition are threads and pipes without dissasembling.

To prevent twisting of valve and second nut need 2 more pipe wrenches, can block them to brick wall.

Somewhat skilled/experienced plumber can do fix without breaking a wall, cant guess You can.

Answer 2

How can I fix this leaking connection

undo it, don't use a union.

But from your pics with the red handled valves having a stainless looking color, if those pieces are stainless (which I suspect they are being a heating system) then threading stainless into brass can be difficult and to prevent leaks you need to use teflon tape and/or [good] dope on the threads. There's all kinds of pex manifolds today, from plastic to brass copper and stainless. Believing the "stainless" ones I see on amazon for ~$100 are stainless... i'd believe EDKH first. Unless you can mention the make/model of manifold and the valves and who installed it... your first pic with the union and shutoff valve... replace with a quality brass valve and don't use a union, and then reconnect the copper pipe. The leaking spot, which looks like a union style nut, is not a traditional union fitting it looks like some b-ized fitting + valve that comes on all those pex manifold kits that offers "easy install". It's not the union mating surface that's leaking. You tighten that stainless threaded valve thing more into the brass manifold the stainless will just nuke the brass threads and you'll need a new manifold.

Answer 3

Here is a brass manifold similar to the "distributor component" with all the branch pipes coming off it in your picture:

source

Notice that the right end of my pictured manifold does not have a brass nut, like your manifold does.

Now notice the extra stuff on the end of this manifold:

source

The stuff on the end attaches with a nut-style connection. My first manifold picture would have other stuff attached to it on the end that at present doesn't have a nut. The nut end of your manifold is where you could try disassembling your system to fix the leak.

I believe that the brass nut holding the silver pipe at the end of your manifold is a "union"-style nut. This is a pipe union:

source

It's designed so you hold on to either of the nut-shaped ends and turn the nut in the middle, and the ends can come apart without rotating the ends. You can try something similar with the brass nut at the end of your manifold.

After depressurizing the hydronic heating system and removing the water from it, try holding the big brass manifold steady and unscrewing the brass nut at the end. If the brass nut loosens and the silver pipe with the pipe sealant can come loose, then apply new sealant or whatever is supposed to seal that joint and reassemble the brass nut. Then re-fill the hydronic system.

These nuts are quite likely the usual "right hand rule" lefty-loosey-righty-tighty style nuts. Loosen and tighten in the usual way: Hold the manifold steady, put a wrench on the brass nut with the handle facing out toward you, and pull down on the wrench handle to loosen.