Inlet filters and main fire pumps: a practical question, but one with direct implications for installation. Let’s see when they are required and where they should be installed, as specified in UNI EN 12845 9.3.6.
Table of Contents
When discussing inlet filters (context of the question)
The requirement is clear: when filters must be installed on the inlet lines of the main fire pumps.
In the context of plumbing practice, a filter is not “always necessary”: it depends on the pump’s inlet conditions and, in one specific case, also on the type of tank (open tank).
Reference: UNI EN 12845 9.3.6
The referenced standard is UNI EN 12845 9.3.6.
According to these guidelines, inlet filters must be installed in two distinct and mutually exclusive scenarios:
- whenever the pumps are installed above the sump (with the filter positioned in a specific way relative to the sump valve);
- only in the case of open tanks, when the pumps are operating below the liquid level (with precise instructions on where to install the filter and with a shut-off valve between the tank and the filter).
Inlet Filters with Overhead Inlet: When Are They Required?
In the case of above-door inlet, the requirement is clear: inlet filters must always be installed.
Furthermore, it’s not enough to simply “install a filter”; the installation location is also specified. The filter:
- It must be installed upstream of the bottom valve.
This information is crucial for anyone who needs to inspect an existing system or properly set up an installation plan: the location is not a matter of choice, but is an integral part of the relevant regulatory requirement.
Intake Filters with Under-Cowl Inlet: When They Are Required
In the case of under-cabinet inlet ventilation, the response is more selective.
Inlet filters are installed only on open tanks. Therefore:
- it is not indicated as “always” for all sub-beats;
- It is explicitly linked tothe “open tank”condition.
In addition to “when,” “how” and “where” are also specified:
- The filter must be installed on the inlet pipe;
- The filter must be located outside the tank.
Where to Install Inlet Filters: “Upstream” and “Outside”
The two operational guidelines that govern the installation are:
- “upstream of the check valve” (overflow scenario);
- “outside the tank” (under-tank scenario with an open tank).
In practice, the answer isn’t just a simple “yes or no” to the filter, but it also clarifies that:
- In the upper chamber, the connection to the bottom valve is part of the installation;
- In the case of a sub-hanger with an open reservoir, the “external” placement is an explicitly required specification.
If you are revising a floor plan or layout, use these two guidelines as a reference for positioning the component in the inlet.
Valves and Shut-Off Devices: What to Include Along with the Filter
In the specific case of open tanks that supply submersible pumps, a dedicated shut-off valve is required in addition to the filter.
It is stated that:
- A shut-off valve must be installed between the tank and the filter.
Therefore, in the basic configuration described, the components are not “just filters”: the shut-off valve is part of the configuration required in that case.
For the inlet above the sump, on the other hand, the bottom valve is used as a positioning reference (with the filter located “upstream” of it).
Common Mistakes to Avoid (Based on the Guidelines Provided)
Without adding any requirements not mentioned here, there are some “logical” errors that this answer helps prevent:
- Confusing the two cases: treating the lower and upper beams as if they followed the same rules.
- In the upper chamber, install the filter without following the instruction to install it“upstream of the bottom valve.”
- In the sub-tank with an open reservoir, place the filter inside the reservoir, even though it is supposed to be placed outside.
- In the open-tank sub-valve, install the filter but omit the shut-off valve between the tank and the filter.
Conclusion (in brief)
Inlet filters on main fire pumps are required in the following cases: always for above-head pumps (with a filter upstream of the foot valve) and only for below-head pumps in the case of open tanks (with an external filter and a shut-off valve between the tank and the filter), in accordance with UNI EN 12845 9.3.6.
