Notice changes, but do not diagnose from them
A new colour, cloudiness, unusual smell or taste, floating particles, or an oily sheen can signal a change in the supply, plumbing or storage tank. These observations are useful to report, but they cannot tell you whether the cause is harmless, harmful, or related to a particular chemical or germ.
Do not taste water to investigate it. If the change is sudden or strong, pause drinking and food preparation with that source while you contact the water supplier or local authority for instructions.
Pay attention to what happened nearby
A pipe break, pressure loss, floodwater, tank damage, sewer overflow, construction or chemical spill can change the risk even when the water still looks normal. Ask whether a local notice applies to your street, building or source.
If neighbours using the same supply report the same change, share the details with the supplier. A shared report helps locate a possible supply issue, but it still does not replace testing.
Use a test that matches the question
Contact a qualified drinking-water laboratory or local water authority and describe the water source, recent changes and possible exposure. Ask which parameters the lab can test and how to collect the sample correctly.
A home test strip or one laboratory result covers only the tests and sample stated on its instructions or report. It cannot rule out every possible contaminant or guarantee that water will remain unchanged.
Choose a cautious next step
Follow any current local advisory. Boiling may be recommended for some microbial concerns, but it does not remove fuel or toxic chemicals. If chemical contamination is possible, use another source that local authorities advise is suitable and ask for specific guidance.
Keep a note of when the change began, which taps or tanks are affected, and any repair or flood event. Share these observations with the supplier or lab rather than trying to identify a contaminant by smell or colour.
Frequently asked questions
Does bad smell always mean water is unsafe?
Not necessarily. Smell alone cannot identify the cause or confirm safety. A sudden or strong change is a reason to stop guessing and ask the supplier or a qualified laboratory.
Can clear water still contain contaminants?
Yes. Some contaminants do not change water's appearance, taste or smell. Follow local advisories and use relevant laboratory testing when there is a concern.
Should I boil water that may contain chemicals?
No. Boiling does not remove fuel or toxic chemicals. Use another source and contact the local water authority for instructions.