Plumbing problem, any ideas?

[BonesyBones]

Both the kitchen sink and the bath are not draining, washing machine struggling to drain too.
Toilet, bathroom sink and dishwasher are fine.

DP had unscrewed all pipes where and found no blockages, same with washing machine filter/waste pipe.

After reading online I poured some bicarbonate of soda and white vinegar down both bath and sink, and chased an hour later with boiling water from kettle. No difference.

Have poured cillit bang drain unblocker down both and poked around with the spikes thinking that comes in the pack, but can't get to anything.

Have also tried hair removal cream just incase.

All of these have been chased an hour later by boiling water, and nothing has worked.

Phoned landlord for a plumber who says if it's anything obviously fixable by us we will be liable for the bill (more than fair as it's been blocked by oil and candle wax in the past when teenage SIL was staying).

I can't think of anything that's been put down either drain. Oil is usually poured into a bottle when cooled to bin and fat scraped straight into bin but nothing has been fried recently anyway.

Would rather avoid the bill if possible so is there anything else we can try? And ideas what may be causing it?

[BonesyBones]

Hi, sorry I'd started a new thread in chat for quicker responses and hadn't realise anyone had been here.

Thanks for the responses. We think everything is backing into the washer. DP trying to sort it now.

[cozietoesie]

Do you know what item shares which pipe?

[wowfudge]

I think the problem may be further down the line - do the things mentioned all feed into the same down pipe or section of drain? Bicarb and vinegar together are useless btw - they fizz up as though there is something dramatic happening, but one is acid and the other alkali so they just cancel each other out.

I'd have one last try with soda crystals, sometimes called washing soda (not bicarb) and put some down the kitchen sink, the bath and the drain outside. Do this at night before going to bed and pour a bit of boiled water down after them to move them down the pipes without washing them out. Then stick a kettle full of boiling water down each first thing the next morning and see if that works.

I suspect you have a grease blockage or something else blocking the drain. Soda crystals are good at cutting through grease.

[BonesyBones]

*spikes thinking = spikey thing