The Coldstream FTO+ filter is NSF P-231, NSF/ANSI 42, 53 and 401 certified. It is designed for tap water, but can also treat certain types of untreated water under strict conditions. This page clearly explains what is possible, what is not recommended, and what to avoid.
All the performance data mentioned on this page comes from independent laboratory tests of the Coldstream FTO+ filter, conducted by Envirotek Laboratory LLC on more than 200 contaminants.
What the filter can treat
Tap water
This is the primary and optimal use. Municipal water is already treated: the filter removes residual chlorine, heavy metals, pesticides, microplastics and pharmaceutical residues. No special precautions needed.
Well water
Compatible, provided the well is not contaminated by industrial or agricultural pollutants at high concentrations. If in doubt, have your water tested before use.
Spring water
A clear spring is generally compatible. Check that it is not located downstream of an agricultural or industrial area.
Surface water: river, lake, pond
The FTO+ filter can treat certain surface waters within the manufacturer's KLT Filtration instructions. This is one of the applications validated by NSF P-231 certification, which tests filters on field water loaded with pathogens.
Strict conditions apply:
- The water must have acceptable turbidity (see Turbidity section).
- No chemical or industrial contamination.
- Temperature between 5 and 30 degrees Celsius only.
- Pre-filtration required if the water is highly turbid.
Under these conditions, the filter effectively removes bacteria (99.9999%), viruses (99.9985%) and cysts (99.94%), results tested in an independent laboratory over 3,000 litres.
Rainwater
Possible if the water is collected correctly: clean surface, closed tank, first rain discarded. Rainwater may contain atmospheric particles and organic matter related to the collection surface. Basic pre-filtration is recommended.
What the filter cannot treat
- Sea water or salt water: The filter does not desalinate. Salt water irreversibly damages the filter elements.
- Industrial or chemically polluted water: Water containing solvents, hydrocarbons, or heavy metals at extreme concentrations. The filter reduces many contaminants but is not designed for massive industrial pollution.
- Water heavily loaded with suspended matter without pre-filtration: Very muddy water quickly clogs the ceramic and reduces performance.
- Water outside the 5-30 degree range: Outside this range, performance is not guaranteed. Below 0 degrees, water freezing in the ceramic pores can irreversibly crack the filter element.
Turbidity: understanding and acting
Turbidity measures the clarity of the water. Turbid water contains particles that quickly clog the ceramic.
Practical guide:
- Clear water (you can see the bottom of a glass): compatible directly.
- Moderately turbid water (river water after rain): let settle for 30 minutes, pour the upper part into the filter. A fine cloth can serve as a pre-filter.
- Very muddy water (flood water, stagnant pond): pre-filtration required. Let settle for several hours, filter with a cloth before use.
If you notice an abnormal slowdown in flow rate, clean the ceramic elements according to the maintenance instructions.
Summary: compatible water sources
| Source | Compatible | Conditions |
|---|---|---|
| Tap water | Yes | None |
| Well water | Yes | Test if in doubt |
| Clear spring water | Yes | Unpolluted source |
| River / lake (clear water) | With precautions | Pre-filter if turbid, away from industrial area |
| Rainwater | With precautions | Clean collection, pre-filtration recommended |
| Very muddy water | Pre-filtration required | Settle and pre-filter before use |
| Sea water | No | Damages the filter |
| Industrially polluted water | No | Avoid at all costs |
If in doubt about the quality of your water source, contact us before use. We'd rather advise you beforehand than have you use the filter in unsuitable conditions.
Official sources
- Official CF163W performance sheet — KLT Filtration Ltd (PDF) — NSF/ANSI 42, 53 and P231 test data conducted by Envirotek Inc, New Jersey USA
- Official manufacturer website Coldstream Filters — KLT Filtration Ltd