Bathroom plumbed badly?

[Helena91]

We have a shared ownership property, at the time we bought it, it was almost 2 years old already and is now 3 years old.
Not really had any issues. But recently I have noticed when I run the hot tap in the upstairs bathroom for more than say half a minute, I hear a dripping noise which sounds like it comes from behind the wall behind the toilet. I am worried that there has been a major mistake made when they plumbed it in the first place. I spoke to the housing company who owns the other half and they said they can't do anything about it.
Surely we are not responsible for tearing out and re doing a bathroom in a 3 year old house?
Thanks for any advice.

[New Home Expert]

The other owners of a shared equity are usually completely uninterested in getting any defect fixed.
Referring the occupant buyer to either the housebuilder or the warranty company.

A dripping noise could be anything from a leak, to just the hot water cylinder filling up or the cold water storage tank filling up.

If you have had a leak after 3 years there would be signs in the house such as damp, condensation in cold weather and mould.

Turn the water off at the mains stop cock and do what you do and see if you hear the dripping. If you don't hear anything it is likely to be just the tank re filling.