Does the smell come from the water or the drain?
An unusual smell near a running tap does not automatically come from the water itself. The waste outlet and nearby plumbing are separate possible sources, while a change in the supplied water needs the water company’s advice. Report the observation without using taste or repeated close sniffing as a test.
Loyal Plumbers · Updated
Discuss your plumbing workKeep a possible gas emergency separate
If the smell could be gas, leave the affected area and call the National Gas Emergency Service on 0800 111 999 from outside. Do not run taps, appliances or other experiments to persuade yourself that the source is a drain. A sewage-like description does not establish the chemical involved or whether the atmosphere is safe.
Carbon monoxide has no smell. An alarm or suspected exposure requires its own urgent response, regardless of what the plumbing appears to be doing. This article concerns how to route a water or waste enquiry once any emergency concern has been addressed; it is not a method for identifying gases by their odour.
Describe what changed without tasting the water
Useful information includes when the change started, which outlet was involved and whether the water also looks different. Note recent supply work, a replacement tap or plumbing alteration if known. Keep those observations factual rather than deciding that a particular material or nearby drain must be responsible.
Do not taste water to investigate a concern or repeatedly lean over the waste outlet to compare smells. Thames Water provides guidance for different smell and taste complaints and can advise on the appropriate next step. If you are unsure about using the water, seek the supplier’s advice rather than rely on a generic online reassurance.
Identify the relevant water supplier
The company providing water-quality advice for the address may differ from the organisation dealing with wastewater. Use the property’s account information or established building-management contact to identify the supplier. For a flat with a shared supply or stored-water arrangement, explain that configuration when reporting the concern.
The supplier may request particular information or checks. Follow those instructions rather than invent a sampling procedure or send an unlabelled household container as evidence. Keep the incident reference and any advice given. This helps a plumber understand what the supplier has established and prevents assumptions that a water-company visit covered private fittings it did not inspect.
Consider the waste side without declaring the water safe
Water entering a basin can coincide with an odour from the outlet or nearby trap. That possibility can justify inspection of the local waste arrangement, especially where the fitting drains slowly or the complaint appeared after a connection changed. It does not, by itself, prove that the supplied water has no problem.
The plumber can identify the trap, inspect accessible connections and consider relevant ventilation or downstream issues. The scope should say what was checked. A local drain repair and a supplier’s water-quality assessment answer different questions; neither should be represented as a substitute for the other when both concerns remain unresolved.
Explain whether the issue follows a recent alteration
A new tap, flexible connector, appliance connection or cupboard arrangement can be relevant to the investigation. Gather the installation date and product information. If several changes happened together, list them rather than focusing only on the part closest to the smell.
The assessment should distinguish an installation defect from a coincidence. For example, a changed waste connection may deserve checking while a supplier is separately assessing a reported change in the water. Do not remove components or add disinfectants to the system before advice is obtained. Altering the installation can introduce another problem and make the original conditions harder to assess.
Coordinate private and shared plumbing access
The relevant supply route may include a communal cupboard, storage arrangement or fittings outside the dwelling. A plumber needs authority and access before investigating those parts. Tell the managing agent about the concern if the system is shared, especially when more than one home reports a similar change.
Ask each person to record their observation and time without encouraging deliberate exposure or repeated testing. The manager can then coordinate supplier and plumbing visits. Avoid sending a contractor into a plantroom or service space without the appropriate arrangements; access to the flat alone may not provide access to the part that needs assessment.
Keep the outcome and remaining questions clear
A useful record distinguishes the supplier’s advice, the private plumbing inspected and any repair completed. If no defect is found in the accessible waste connection, that is a limited result rather than proof about all concealed pipework. If the supplied water remains in question, continue through the supplier’s advised process.
Loyal Plumbers can assess private plumbing and waste connections across London and inside the M25. Include the affected outlet, timing, recent changes and any supplier reference in your enquiry. We can request reports or photographs by email afterwards. The right outcome is a clear next step with the appropriate organisation, not an unsupported declaration that an unusual smell is harmless.
Common questions
- Should I assume a rotten-egg smell is just the drain?
- No. Odour alone cannot safely establish the source. Address any suspected gas emergency promptly and seek the water supplier’s advice for a possible water-quality concern.
- Can a plumber confirm the water is safe by inspecting a tap?
- An inspection can identify relevant plumbing defects, but it is not a substitute for the appropriate water-quality assessment or supplier advice.
- Who do I call if only one outlet seems affected?
- Explain that pattern to the water supplier if water quality is in question. A plumber can assess the local private fittings and waste arrangement; one affected outlet does not settle the cause by itself.
Sources and further reading
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