Any ideas how to fix this leaky tap and what the part is called?

[rossmcd]

We have a sink tap where the rubber washer between it and the sink has degraded and causes a slight leak into the cupboard below. All very straightforward so far. But since that started, the tap can be twisted left or right and water is ALSO definitely leaking from the nut in picture 2.

This is underneath. I have tried twisting the nut both ways, and both ways increases the leak.

Any ideas how to fix this and if I need to replace that part, what is it called?

Many thanks in advance!

 

[oldbuffer]

1. That's what is known as a three hole tap. I find them difficult to work on.
2. Unless you are a pretty experienced DIYer and have a good set of tools, I'd recommend getting a plumber to do it.
3. If you intend to DIY it you are likely to have to do a fair bit of dismantling to get at various bits:
3.1. Isolate hot and cold water.
3.2 To fix leak through central spout to underside of cupboard you are going to need to tighten the large brass nut securing the spout. Looks difficult to access with special tools such as Armeg "jaw droppers" or Nerrad "Tapex". Without these (and possibly with them) you would need to disconnect and remove the chromed horizontal pipe between that threaded shank of the spout and the right hand tap to gain access.
3.3 If tightening the nut doesn't stop that leak you will have to remove the spout and replace the rubber washers. This may require removing the pipe between the spout and the left hand tap.
3.4 Fixing the red circled leak depends on how the pipes to the right and left of it are secured, and how the bit with the chrome hexagon on it is secured to the threaded shank of the tap. Likely to require removal of both left hand an right hand horizontal pipes.

 

[oldbuffer]

An update to my previous post. Armeg "jaw droppers" do not have a spanner to fit the spout's back nut so not suitable for that part of the job.