We live in a Victorian terrace that has a back yard.
Next door neighbour has the same plot/house but they had their yard concrete torn up and grass put down to make a garden.
We are on really good terms with them and our kids play together.
Sometimes we go round for dinner and they come to us.
A really bad drain smell started in theirs about 2 years ago. We noticed it at first (thought it was ours) but quickly realised it was from theirs.
One night we were in their garden having dinner and the smell happened (I honestly don't know how they cope with sitting in their garden, it's that bad) and they looked sheepish and apologised and said that when they had the work done to the garden somethings went wrong and now they have this smell whenever their washing machine/sink (or something like that) is on. But they said it's super expensive to fix as it involves lifting their garden and digging quite deep.
They asked if we could smell it and we said yes. They said something like 'we need to get that sorted but it's so expensive'
This was over a year ago and since then one of them has been made redundant but the smell is much worse and they're in the house more working from home and so using their sink/washer more.
It feels like every time I open my back door it stinks, it's a really grim drain smell, and because the weather is warmer I want the door open more.
I just feel so guilty asking them to sort it as they are skint, but it's bothering us.
Any ideas on what my rights are over smells, and how I can diplomatically nudge them.