A filter’s backwash flow requirement is only comparable with supply recorded at the applicable inlet conditions for the required duration. Use the exact assembled-system requirement, not a valve’s maximum capacity or a generic tank-size estimate. The checker below keeps missing pressure, duration, configuration, temperature and drain information visible.
Can your supply meet the entered backwash requirement?
Start with the exact assembled-system requirement
Identify the complete model and configuration, the installed media, tank and valve arrangement, the relevant cycle, and the document revision or supplier clarification. Record the source page so a later reader can reproduce the requirement. If the documentation gives a range, do not silently choose its lowest value; establish the value applicable to the proposed configuration.
| Documentation | Useful for | Limit |
|---|---|---|
| Exact assembled-system manual / written supplier clarification | Applicable minimum flow, pressure, duration and installation conditions. | Must match the actual configuration and relevant commissioning or routine cycle. |
| Valve specification | Component capacity under a stated pressure-loss condition. | A maximum component capacity is neither your supply nor the assembled filter’s required flow. |
| Media documentation | Media-specific loading and operating information. | A loading rate per square foot is not a complete equipment compatibility decision. |
| Pump documentation or well record | Understanding the supply equipment or a recorded well assessment. | Does not independently establish flow delivered at the intended treatment inlet. |
Document scope matters. The Watch-Water Katalox Light operation manual, document #140513KL-OPM, page 1, distinguishes initial conditioning from regular backwash. It is media documentation hosted by a distributor, not a validated preset for every assembled Katalox system. This checker supplies no generic media or tank-size presets.
Document example: a 10 × 54 Katalox filter and a six-GPM supply
The Genesis Katalox manual, printed page 5, lists GENKAT15 (10 × 54 tank) at 7 GPM backwash and GENKAT20 (12 × 52) at 10 GPM. If the GENKAT15 requirement applies, a comparable 6 GPM supply is 1 GPM short on flow alone. Do not generalize that row to every 10-inch filter.
Minimum inlet pressure is not pressure drop across a valve
A manufacturer’s valve flow rating describes a component under stated conditions. Pentair’s Fleck 5600 filter-valve page lists a maximum backwash flow of 7 GPM at a 25 psi drop. Its Fleck 2510 page lists 17 GPM at the same stated drop. Neither number is a measurement of your well, and the 25 psi pressure-loss condition is not a universal minimum inlet-pressure requirement.
The checker asks for the exact system’s documented minimum inlet pressure and the lowest observed pressure under comparable flow conditions. It does not calculate pipe losses, drain backpressure, valve sizing or the maximum permissible pressure. Those remain separate installation checks.
How to read the result
| Outcome | What triggered it | Your next decision |
|---|---|---|
| Insufficient information | A required record is absent; observation is shorter than the entered cycle; or one of the applicability confirmations is unresolved. | Obtain the missing evidence. A positive numerical flow difference does not resolve missing conditions. |
| Below an entered hydraulic requirement | Comparable records are complete, but observed flow or minimum pressure is below the entered minimum. | Ask the supplier and qualified professional to assess the mismatch before selecting this configuration. |
| Entered hydraulic comparison met — installation not approved | Complete comparable records meet the entered flow and minimum-pressure thresholds for the stated duration. | Verify remaining manual conditions, reserve needs, chemistry, service flow and installation requirements. |
The flow difference is supply minus the entered requirement. Equality provides zero difference; it creates no reserve. This tool does not invent a percentage safety factor. Its result depends on the accuracy of the records and confirmations you provide.
A flow rate and a cycle’s water volume answer different questions
Total cycle water = sum of each documented cycle’s flow × duration
A hypothetical constant 6 US GPM for ten minutes requires 60 US gallons for that backwash cycle. The calculator excludes any rinse, regeneration, refill or other cycle not entered, plus household demand. It also does not establish that the supply can deliver the calculated volume at the required pressure.
A pressure tank’s nominal gallons cannot be used as the same number of available backwash gallons. Amtrol’s model and drawdown table illustrates that distinction. Storage arrangements, usable volumes and booster delivery need their own assessment. See the rate-versus-cycle-volume guide for the arithmetic distinction.
Three worked examples: the same rate can give different conclusions
| Hypothetical record | Result | Reason |
|---|---|---|
| 6 GPM at minimum 40 psi for 30 seconds; requirement 6 GPM, 30 psi, ten minutes. | Insufficient information. | The 0.5-minute observation is shorter than the ten-minute cycle. |
| 6 GPM at minimum 25 psi for ten minutes; requirement 6 GPM, 30 psi, ten minutes; all conditions confirmed. | Below an entered hydraulic requirement. | The flow equals the minimum but the observed pressure is 5 psi below it. |
| 6 GPM at minimum 40 psi for ten minutes; requirement 6 GPM, 30 psi, ten minutes; all conditions confirmed. | Entered hydraulic comparison met; installation not approved. | Flow meets the entered minimum with zero flow reserve; other requirements remain separate. |
These invented numbers demonstrate the decision rules. They are not recommended pressure settings, manufacturer requirements or measured household results.
Questions to send to the supplier before buying
- Which complete model and media/tank/valve configuration does this requirement apply to?
- What flow and inlet-pressure conditions apply during each backwash and rinse cycle?
- Are commissioning requirements different from routine backwash?
- Which water-temperature conditions change the requirement?
- What drain restrictions, routing and disposal conditions must the installer verify?
- What chemistry, service-flow and maintenance limits remain outside this comparison?
Keep the written answers with the manual revision and relevant supply record. A vague assurance that a pump is “big enough” does not provide a reproducible comparison.
Questions about well-pump and filter backwash compatibility
Can a six-GPM well run an iron filter?
That number alone cannot settle it. You need the exact system requirement and comparable evidence of delivery at the relevant pressure and duration. The filter’s chemistry and treatment-performance limits need separate assessment.
Can tank diameter tell me the required backwash GPM?
Tank area and a documented media loading rate can support a scoped calculation, but they do not by themselves establish complete-system compatibility. This checker does not turn a diameter into an installation approval.
Does a lower drain-flow control make an undersupplied filter acceptable?
This tool cannot authorize that change. A configuration must meet the assembled system’s documented operating requirements; ask the supplier and qualified installer about any proposed modification.
Why does unknown drainage keep the result unresolved?
A flow number is only part of the decision record. Drain routing, discharge capacity and applicable disposal requirements need separate verification; this tool does not infer them from inlet flow.
Can I use a bucket observation from F2 here?
Only when appropriate supporting observations establish sustained supply under the applicable conditions. F2’s volume-and-time result alone is an interval average.
Sources and review status
Source check: 6 October 2026. Documentation supports the distinctions above; it does not validate user-entered requirements. The checker has software verification for its calculation and uncertainty rules. Independent professional validation of a measurement or installation procedure has not been completed.
Record a flow observation · Methods and source register · Why a valve rating is not your available flow