Are you using Coldstream FTO+ filters and looking for an alternative for your gravity fountain? Discover the new filters Monderma Imperial GF and AMB, made in the USA. Two versions to choose your filtration technology while keeping your fountain, subject to compatibility with your model.
Which alternative to choose: Imperial GF or AMB?
- Imperial GF: ceramic, activated carbon in granules and zeolite, with an indicative flow rate of 3 L/h for two filters.
- Imperial AMB: ceramic, block of compressed activated carbon and zeolite, for filtration through two successive porous structures.
Both versions are offered in sets of two, with an announced autonomy of up to 12 months and an indicative capacity of 6,000 liters per pair. These values depend on the water used and the conditions of use.
The advantages of Imperial filters to replace your FTO+
1. Made in the United States
The Imperial GF and AMB are made in the United States. Their country of manufacture is indicated in their product sheets. This is an original difference with the Coldstream FTO+, manufactured in the United Kingdom; Origin alone does not constitute proof of superior performance.
2. Potentially less frequent replacements
Imperial files advertise up to 12 months of use for a pair, compared to a deadline of 6 months for FTO+. The capacities indicated are 6,000 liters per Imperial pair, compared to 1,500 liters per FTO+ element, or 3,000 liters for two elements.
These indications can allow you to space out refill purchases. They do not guarantee the same duration for all waters: respect the volume limits, deadlines and instructions in the instructions. The figures come from the product sheets and do not constitute a comparative test under identical conditions.
3. Two technologies to choose your configuration
The GF retains a combination of ceramic and coal in granules, supplemented by zeolite. The AMB offers another architecture: after the ceramic, the water passes through a block of compressed activated carbon.
This difference allows you to choose between two filter designs. It does not mean that one systematically eliminates more contaminants than the other: the results must be examined substance by substance, under the test conditions.
4. A cleanable exterior surface
The ceramic of both versions can be cleaned according to their instructions to remove surface deposits. On the AMB, gentle cleaning in cold water with a non-abrasive sponge is indicated when the flow rate decreases.
Cleaning the ceramic does not regenerate the activated carbon and does not reset the life of the filter. This maintenance option also exists on FTO+.
5. The possibility of keeping your fountain
The Imperial files mention in particular the Monderma, Berkey, British Berkefeld and ProOne gravity systems. The replacement concerns the filter elements: it does not require changing the tanks when the assembly is compatible.
Check the exact model, available space, mounting holes and gasket mounting. The announced size of the Imperial is 7 inches high and 2.75 inches in diameter. The brand name of your fountain is not enough to guarantee the compatibility of all its models.
6. Gravity operation
Like the FTO+, the Imperials are intended for systems operating by gravity, without power supply to the filter and without pressure connection. They are thus integrated into the usual operation of a compatible two-tank fountain.
Comparison Coldstream FTO+ / Imperial GF / Imperial AMB
| Criterion | Coldstream FTO+ | Imperial GF | Imperial AMB |
|---|---|---|---|
| Manufacturing | United Kingdom | United States | United States |
| Technology | Ceramic and coal in pellets | Ceramic, granulated carbon and zeolite | Ceramic, compressed carbon block and zeolite |
| Announced deadline | 6 months | Up to 12 months | Up to 12 months |
| Indicative capacity for two filters | 3000L (2 × 1500L) | 6,000L | 6,000L |
| Advertised flow | 1 L/h per element | Around 3 L/h for two elements | Approximately 4 L in 2 hours, then slowdown, depending on configuration |
| Cleanable ceramic | Yes | Yes | Yes |
| Use | Gravity, no pressure | Gravity, no pressure | Gravity, no pressure |
| Sheet and current price | See the FTO+ | See the Imperial GF | View Imperial AMB |
The flow rates are not presented on an identical basis of measurement: a flow rate per element, a flow rate per pair and a cumulative volume do not constitute a speed classification. Water level, maintenance and configuration influence flow rate.
Filtration performance: view detailed results
Our Imperial sheets announce tests carried out by Envirotek Laboratories according to NSF/ANSI protocols 42 and 53. They detail the announced performances for different contaminants.
A test according to a standard and a product certification are two separate pieces of information. To choose based on a specific contaminant, consult the report corresponding to the filter reference, with the concentrations tested, the volume treated and the test conditions. Contact us to obtain the elements available on the filter that interests you.
What is the best alternative for your use?
Choose the GF if you are looking for the Imperial version with granulated activated carbon, with its indicative flow rate of 3 L/h per pair.
Choose AMB if you want a design combining an exterior ceramic and a compressed activated carbon block. Plan for a slowdown in flow during filtration.
In both cases, the choice must take into account your consumption, the quality of your water and your fountain. A longer announced autonomy is not enough to demonstrate a better reduction of each contaminant.
Before replacing your filters
- Identify your fountain and the reference of your current filters.
- Check mounting compatibility and choose GF or AMB.
- Install and prepare the new elements following their instructions.
- Note the installation date and track deadlines as well as the volume processed.
Imperials are intended for cold water and non-pressure gravity systems. For well water, spring water or microbiologically unknown origin, ask for advice appropriate to its analysis before use.
Find your new Imperial filters
Imperial GF — See the set of 2 and its current price
Imperial AMB — See the set of 2 and its current price
Any doubts about your model? Contact our team before ordering.
Comparison established on September 14, 2026 from the linked product sheets. The capacity and autonomy indications depend on the conditions of use. Coldstream and other brands mentioned are the property of their respective owners.