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Our kitchen/bathroom wastewater flows into an outside drain which tends to overflow,especially if the bath/shower is used.The man who's fitting our new bathroom also noticed this and suggested we may have a leak in the drainage system.There is also a crack in the masonry near the drain.

My other half has tried to clear the drain manually with caustic soda which resulted in a bad smell (like rotten eggs)around the house after.Now he's talking about using sulphuric acid to clear it.I'm against this not only from an environmental (and H&S)standpoint but also in case this causes permanent damage to the drain.Can anyone advise on what our next steps should be? Thanks.

"Our kitchen/bathroom wastewater flows into an outside drain which tends to overflow,especially if the bath/shower is used."

Its blocked up.


"The man who's fitting our new bathroom also noticed this and suggested we may have a leak in the drainage system. There is also a crack in the masonry near the drain."

Actually your problem is that its blocked up. Crack in cement around drain prolly nor relevant.


"My other half has tried to clear the drain manually with caustic soda which resulted in a bad smell (like rotten eggs)around the house after.Now he's talking about using sulphuric acid to clear it."

Caustic soda (akali) and Sulphuric Acid (acid) are an explosive and I mean seriously explosive, combination. That would be silly.


"I'm against this not only from an environmental (and H&S)standpoint but also in case this causes permanent damage to the drain.Can anyone advise on what our next steps should be?"

You are correct and the water company won't be that happy at all. He needs to get his marigolds on and do it manually because its probably in the trap. Its prolly largely a mixture of soap scum and congealed fat. I suspect it will clear with a little ferreting about - won't be pleasant mind.

Check it out in the reverse direction from the nearest manhole it may need rodding or failing that jetting.

Cheers