Awful smell of drains - help!

[Cambionome]

We have a downstairs shower room and toilet - which is very handy - but I've occasionally noticed a slight smell of drains. Just recently the smell has got a lot worse and is, on occasion, pretty awful (though sometimes non-existent).

Has anyone got any thoughts? Is there anything I can put down toilet (it doesn't seem to be blocked but I assume there must be some kind of a blockage somewhere?) Or do I have to bite the bullet and pay for someone to look at it?

Thanks in advance!

Try drain clear stuff in the shower plug first. Have you taken the shower plug up to check the trap isn't blocked, is it a bit slow running?

Anyway, use the drain stuff (from any supermarket) first. It's more likely to be that than the loo. Though it could be the loo, eliminate the cheap things first. A dislodged or cracked stench pipe would cause it but can be hard to find and repair.

Our second shower hardly gets used, and the water in the trap below the plug hole evaporates, and we get a drain smell. It goes when I run some water in.

Thanks very much for the replies! The shower gets used at least twice a day, but I will try drain stuff down it. I hadn't even thought about it being the shower, just assumed it was the loo!