Leaking towel rail

[mo2]

Last sunday, the heating went off because of a pressure drop in the system, we had no idea where the problem was, but switched it back on. On wednesday, we discovered the pipe leading up to the new(ish) towel rail was leaking very slowly it looks like a loose nut(correct name?), I think I have the tool to tighten it, but wanted to check to be sure, because I have not done any plumbing before

The bottom part, is the part leaking

tighten with this?

 

[Fluffster]

You can use the grips to hold the main body of the isolation valve as you use an adjustable spanner to tighten the nut.
Pete

 

[mo2]

ok, will get the spanner out

 

[sime10]

Hold against it with another spanner tho you may get a gush