Understanding Drain Smells (Eggs, Fish, Sewage & more!)

Pig nose sniffing smells

Do you notice a nasty smell emitting from your drain? The causes are varied, and solutions range from a quick fix to an emergency callout. Whether your drain stinks of egg, urine, sewers or fish – this guide will cover some of the most common reasons for a smelly drain. It is also important to note, sometimes the odour can come from somewhere else other than a drain, and these causes will also be addressed in this guide.

See also this article about drain bad smell.

A CCTV drain survey can easily diagnose the problem by delving deep into the drain system and rooting out the cause.

Why does my drain smell of egg or sulphur?

If a less-than-pleasant egg or sulphur smell is coming from your drain, this could be caused by an unused drain, contaminated drain or water, a lack of a trap, or a clogged vent.

  • An Unused Drain: Perhaps you have been away on holiday and not used your drainage system in a while? This can cause drainage water in the trap (a bent part of the pipe that seals against gases entering your home) to evaporate, destroying the seal effect and causing gases to travel back into the building. Simply turning the tap on and letting the water run for a minute, or flushing a toilet, can be a quick fix for this.
  • No Trap: It could be that you have no trap at all. This is a structural issue, and one that a plumber will need to resolve.
  • Clogged Vent: An obstruction in a plumbing vent can cause smells to creep back into your building. In the future, placing screens over your vents can bypass this issue.
  • Your Pipes Need Disinfecting: Hair, skin and other debris can build up in pipework, emitting an odour. Sometimes, all it takes is a thorough disinfection of the affected pipe to solve the problem.
  • Contaminated Water: Smelly water may be a result of the water source itself, which could have become contaminated by drain parts.

Why does my drain smell of sewage?

Sewage smells are extremely unpleasant and can be caused by broken toilet seals, dry traps, cracked drain elements or a clogged vent system.

  • Broken Toilet Seal: Check around your toilet, including near the u-bend. Any damage to the toilet seals could be allowing these pungent smells to escape into your property.
  • Dry, Missing or Ineffective Trap: All drains have a trap to stop sewer gas from entering a property. If this trap is dry, it is unable to perform its duty, so a simple mend consists of pouring water into the drain. If this does not work, your trap may be damaged or ineffective. An expert drain survey can confirm this for you.
  • Debris in Inner Chamber: This tip mostly applies to kitchen sinks, often which have an inner chamber. It is here that debris can collect, so clear this area and notice if the smell subsides.
  • Sewer Gas Leak: Whether it is cracked pipes or traps, or loose fittings, sewer gas leaks are bad news. Narrowing down their origin can be tricky, and may benefit from a comprehensive drain survey delivered by trained engineers.
  • A Blocked Vent: The blame could lie with your vent system. If this becomes clogged then smells cannot escape outside, and instead will build-up within the property.

Why does my drain smell of urine?

If a drain is emitting a strong urine smell, then a faulty toilet seal or mould problem could be the reason.

  • Faulty Toilet Seal: Every toilet should have an effective seal ring. Should this be faulty or missing, this could result in the lingering urine smell. This should be fixed by a quick call to a plumber.
  • Mould: One culprit could be mould, in or around the bathroom area. The mould could potentially be hidden underneath wall tiles or lino, so check these out-of-sight areas, too.

Why does my drain smell of fish?

If your kitchen or bathroom is reeking of fish, despite the lack of fish in that area, this could be an indication of a sewer gas leak, poor water quality or an electrical fault.

  • Sewer Gas: The location of the sewer gas could be varied e.g. a neglected drain, or the venting system. A professional surveyor can root out the problem, and identify the area of your plumbing system where the sewer gases are emanating from.
  • An Electrical Fault: The scent may actually not be coming from a water source, as suspected. A described ‘fishy’ smell could actually be the plastic of electric wires overheating. If suspected, this should be dealt with immediately. Electrical fires could mean destruction and injury, so bring in a professional to check out your home electrics.
  • Poor Water Quality: If the scent transpires to be neither of the above options, the issue could lie with the quality of your water. Take this up with your local water company who should be dealing with concerns of this nature – they may test your water quality for you.

Don’t ignore a smelly drain – a specialist CCTV drain survey can help diagnose drainage problems by taking a look at what’s going on in the pipework. Here at Express Drainage Surveys, we cater for both domestic and commercial clients, using the latest technologies to deliver drainage surveys to accurately identify issues. Get in touch today to discover more – we’re happy to help.