When to Retest
A single test is a snapshot. Water quality changes seasonally, products get reformulated quietly, and filters degrade. Know when to retest so you are not relying on stale data.
Event triggers
New home
Test immediately. Different plumbing age and materials mean different contaminant profiles.
Product reformulation
Label changes, new packaging, or brand acquisition = request fresh COA. New supplier sourcing can introduce contaminants.
Contamination event
Boil advisories, chemical spills, flooding, construction. Test after resolution and again 30 days later.
Filter replacement
Test after new filter install to confirm it works. Test again as filter approaches rated lifespan.
Seasonal factors
Spring runoff: snowmelt increases ag runoff. Nitrates, pesticides, turbidity spike. Well water users: test late spring.
Summer heat: accelerates bacterial growth, increases disinfection byproducts. Chloramine and THM levels peak.
Post-drought: disturbed sediment releases metals and particulates into supply.
Minimum retest schedule
City water (no concerns): every 2-3 years
City water (old home): annually for lead and copper
Well water: annually for bacteria/nitrates, every 3 years for full panel
Filtered water: after each filter change, then mid-lifespan
Supplements/products: request new COA with each new batch or annually