The shower in our guest bathroom doesn't get used often, so I suppose soap etc sits in the outlet pipe for ages then, when the shower IS used, it stirs it all up. The smell is awful. I've tipped several kettles of boiling water down, and a whole bag of washing soda. I've now got a load of bleach down there which I'll flush down with more boiling water , but is there a product that might help? Any good tips?
I think the problem's compounded by the fact it's on the ground floor so not a huge 'drop' for gravity to carry stuff away.