Smelly plumbing after loft conversion

[AuntieJune]

We had our loft done, completed a few months ago. There's a shower and toilet in an ensuite, macerator and soil pipe that comes through the house and links up with the bathroom soil outlet at the back of the house.

The builders we used were shit and bodged other stuff up, they've gone bust so no come back at them. We're having to sort out other things they did badly.

The plumbing smells a bit, and never did before - drain type of smell. Can't see any leaks or anything.

What do I do? Can I get a plumber out just because there's a smell?!

Not a loft conversion but we had smelly plumbing on the top floor of our townhouse. There was a one-way air valve at the top of the soil pipe that had failed, so we were getting smelly toilet gases leaking into the roof space. Needed a plumber to replace it, so yes you can call one just for a smell!

Air is getting out of the drain system, as pp said possibly a failed air admittance valve or if they were complete cowboys they haven't put in a trap somewhere.

Plumber is what you need!

Thank you. Next time I'll choose better builders!

We had this, they hadn't put the right vent on the outflow pipe.

Probably the macerator sucking water out of the shower trap, they're very swallow.

Fitting (or replacing) an air admittance valve before the macerator will cure it.

Thanks @Surplus2requirements

Would it only smell in the loft then? It smells there but also in other places in the house, including ground floor

@AuntieJune if there's no leak then the smell has to come from where there is an inlet into the system ie shower drain sink waste etc where a trap should prevent air returning into the room.

Because of its nature we can become very attuned to the smell once we identify it which may explain noticing it in other areas.

It's also possible you have a hidden leak that you haven't identified yet.

Tbh I avoid macerators wherever possible, foul water under pressure is not a great combination and clearing a blockage in the macerator itself is a nightmare but I realise that sometimes there's no option. Make sure wipes NEVER get flushed.

If you can't identify precisely where the smell is coming from (after flushing toilet check sink and shower) I'd get a plumber to check how they've plumbed the system and that you haven't got a partial block which can cause syphoning elsewhere in the house.