I live in ground floor flat in a block of 3 storeys. I had a sewage back flow when main sewers were blocked due to solids down the toilets. I want to install a check valve to prevent back flow. As I don't know the sewage pipe routing for the building I want to install the check valve in the toilet next to the pan.
Can someone suggest the best type of check valve for this purpose (it needs to be compact). Also maybe suppliers or fitters who can provide this type of valve.