Coliform and E. coli water test
This is the short answer to "is my water safe to drink right now". Total coliforms indicate that something is getting into the water that should not be; E. coli indicates specifically faecal contamination. Both must be absent in drinking water. It does not cover chemical safety — arsenic, lead and fluoride need separate tests.
What this test does and does not tell you
The cheapest useful water test, provided you understand its boundary. Pair it with a short chemical panel if there is any health concern.
| Question | Answered by this test? | If not, test for |
|---|---|---|
| Is sewage or surface water getting in? | Yes | — |
| Has the overhead tank been contaminated? | Yes | — |
| Is the water causing stomach illness? | Likely indicator | Add a pathogen screen if illness is confirmed |
| Is there arsenic in my borewell? | No | Arsenic, specifically |
| Is lead leaching from old plumbing? | No | Lead, first-draw sample |
| Is the fluoride level safe for children? | No | Fluoride |
| Why does the water taste metallic? | No | Iron and manganese |
| Is my RO unit working? | Partly | TDS, hardness plus this test |
What to send us
Why the result takes two days
Bacteria have to be grown before they can be counted. The incubation period is fixed biology, not queue time — a laboratory offering a same-day coliform result is either doing a rapid presumptive screen, which needs confirmation, or not doing the test. If you need the answer faster, tell us and we will explain what a presumptive result can and cannot be used for.
Questions about this test
My RO vendor says my water is fine. Should I still test?
A vendor’s TDS meter measures dissolved solids, which is not a safety measurement. It says nothing about bacteria or metals. If the vendor is also selling the remedy, an independent test is worth its cost.
Coliform present but E. coli absent — how bad is that?
It means contamination is entering the system but there is no direct evidence of faecal origin. Common causes are an uncleaned tank, a cracked cover or biofilm in the plumbing. It needs fixing, but it is a different urgency from an E. coli positive.
How often should a household test?
Once a year for a stable municipal supply, and after any event that could let contamination in — tank cleaning, plumbing work, flooding, or a change in taste, smell or colour.