When the Required Tank Capacity Does Not Fit the Building
- The engineer has calculated the required storage volume.
- The building design is moving forward.
- Then a practical problem appears.
- The tank does not fit.
- A standard cylindrical water tank may provide the required capacity, but its diameter, height, or access requirements can make installation impossible inside a mechanical room, parkade, basement, podium, or high-rise building.
This is a common challenge on projects where available floor area is limited and every part of the building has already been allocated.
The solution may not be to reduce the required storage capacity.
Instead, the tank can be designed around the available space.
Custom fabricated plastic tanks can use rectangular or project-specific dimensions to help engineers fit water, rainwater, wastewater, or stormwater storage into locations where standard tanks cannot work.
Why Large Tanks Become a Problem Inside Buildings
Tank selection often begins with one number: required volume.
For example, a project may require several thousand gallons of stormwater detention or water storage.
A designer may initially look for a standard tank with that capacity.
But volume alone does not determine whether a tank will work.
The building may have:
- Low ceiling height.
- Closely spaced structural columns.
- Limited floor area.
- Mechanical equipment surrounding the proposed tank location.
- Restricted door or corridor dimensions.
- Pipes, ducts, sprinklers, and electrical equipment competing for space.
- Limited installation or maintenance access.
- Structural or seismic requirements that must be considered.
This is where standard tank dimensions can become a major limitation.
A 5,000-gallon tank may technically provide the correct volume, but that does not help if the tank cannot fit between the building columns or pass through the available access route.
For architects, engineers, contractors, and developers, the real question becomes:
How can we maintain the required storage volume while changing the tank geometry to fit the building?
1. Start With the Required Water or Stormwater Storage Volume
The first step is still capacity.
The project team needs to establish the required working volume based on the building's water, rainwater, wastewater, or stormwater design requirements.
For a stormwater detention system, for example, the engineer may already have a defined storage requirement.
Once that capacity is known, avoid selecting a tank solely by looking for a standard gallon size.
Treat the required capacity as the starting point.
The next step is determining the physical envelope available for the tank.
2. Measure the Available Tank Envelope
Before choosing a tank shape, define the maximum space available.
Record the available:
Length × Width × Height
But do not stop with room dimensions.
A useful tank layout should also identify:
- Structural columns.
- Walls.
- Doors.
- Beams.
- Mechanical equipment.
- Electrical panels.
- Pumps.
- Piping.
- Drains.
- Floor slopes.
- Required service clearances.
- Access areas.
For a mechanical room water tank, for example, a rectangular footprint may allow the tank to sit along a wall while leaving space for pumps and other equipment.
In a parkade, the tank may need to fit between structural columns while maintaining vehicle, equipment, piping, and maintenance clearances.
The objective is to identify the actual usable envelope rather than simply measuring the room.
3. Consider a Custom Rectangular Water Tank
Standard cylindrical tanks work well when sufficient space is available.
But cylindrical geometry can leave valuable floor space unused.
A custom rectangular water tank can use the available building footprint more efficiently.
Instead of asking:
"What standard 5,000-gallon tank will fit here?"
the project team can ask:
"What tank dimensions can provide approximately 5,000 gallons within this available space?"
That change in approach can open additional design possibilities.
A fabricated tank can potentially be configured around:
- Available floor dimensions.
- Ceiling restrictions.
- Building columns.
- Adjacent mechanical equipment.
- Required connections.
- Maintenance access.
This can be particularly useful for:
- High-rise buildings.
- Commercial developments.
- Parkades.
- Mechanical rooms.
- Basements.
- Podium structures.
- Institutional buildings.
- Industrial facilities.
Custom geometry gives the project team another variable to work with instead of forcing the building layout around a predetermined tank diameter.
4. Coordinate Tank Connections Before Fabrication
Making the tank fit the room solves only part of the problem.
The tank must also work with the rest of the system.
Inlets, outlets, overflows, drains, vents, instrumentation, and access points should be coordinated with the project's piping and equipment layout.
Depending on the project, a custom fabricated tank can incorporate project-specific features such as:
- Flanged inlet and outlet connections.
- Overflow connections.
- Bottom drains.
- Internal plumbing.
- Access hatches or manways.
- Sensor connections.
- Level instrumentation connections.
- Baffles.
- Custom fitting locations.
This can reduce the need to design the piping system around fixed connection locations found on a standard tank.
For mechanical and civil engineers, this is an important advantage.
The tank becomes part of the overall system layout instead of being treated as an isolated piece of equipment.
5. Check Whether the Tank Can Actually Enter the Building
A tank can fit perfectly in its final location and still be impossible to install.
This is one of the most important questions to ask early:
How will the tank get from the delivery truck to its final position?
Review the full access path.
Check:
- Exterior openings.
- Loading areas.
- Doors.
- Elevators.
- Corridors.
- Stairways.
- Parkade entrances.
- Temporary construction openings.
- Turning radius.
- Overhead clearance.
This becomes especially important during building retrofits.
An existing large tank may have been installed before walls, doors, or mechanical systems were completed.
Years later, the old tank can potentially be removed in pieces, but the replacement tank cannot pass through the same building.
At that point, searches often change from:
"5,000 gallon water tank"
to questions such as:
"tank that fits through doorway", "tank assembled on site", "sectional water tank", "retrofit water tank for mechanical room"
That is a different engineering problem.
6. Consider a Site-Assembled Water Tank for Restricted Access
For appropriate projects, a large fabricated HDPE tank can potentially be manufactured in sections and completed at the installation location.
This can help when a finished tank would be too large to move through the building.
Instead of moving one complete tank through a restricted doorway or corridor, the installation strategy can be considered as part of the tank design.
This can be valuable for:
- Existing mechanical rooms.
- Basement retrofits.
- High-rise buildings.
- Restricted-access industrial facilities.
- Parkades.
- Buildings where large exterior openings are no longer available.
The important point is to discuss access restrictions with the tank manufacturer early.
Do not wait until the tank is fabricated to determine whether it can reach its final position.
7. Design the Tank Around the Building, Not the Building Around the Tank
This is where custom tank fabrication provides the greatest value.
Standard tanks come with predetermined dimensions.
A fabricated tank allows the project team to begin with the building constraints.
For example, imagine a project that needs substantial stormwater storage inside a parkade.
The available area may include:
- A maximum tank height because of overhead services.
- A narrow width between structural columns.
- A longer unused area along a wall.
- Several required piping connections.
- Limited installation access.
A standard round tank may fail because of its diameter.
A custom rectangular stormwater tank could instead use more of the available length while staying within the permitted width and height.
The required capacity remains the objective.
The geometry changes to help achieve it.
Custom Stormwater Tanks for Parkades and High-Rise Buildings
Stormwater storage can create particular challenges in dense commercial and residential developments.
The required storage capacity may be substantial, but underground building space is expensive and heavily coordinated.
A parkade stormwater tank may compete for space with:
- Parking stalls.
- Mechanical rooms.
- Electrical rooms.
- Structural columns.
- Plumbing.
- Fire protection systems.
- Building services.
Moving the tank to another location may not be practical.
Reducing the tank capacity may not satisfy the project's requirements.
A project-specific tank therefore becomes another option for the design team to evaluate.
BARR Plastics has worked on this type of application in Vancouver, where required stormwater storage capacity had to be reconciled with the physical limitations of a constrained parkade.
Projects like this demonstrate an important principle:
The tank should be considered part of the building design early enough that capacity, geometry, piping, access, and installation can be coordinated together.
Standard Tank vs. Custom Fabricated Tank
A custom tank is not necessary for every project.
If a standard tank provides the required capacity, fits the space, fits through the building access route, and has suitable connections, it may be the simplest solution.
A custom fabricated tank becomes more valuable when the project has constraints such as:
| Project Constraint | Why a Custom Tank May Help |
| Limited floor space | Rectangular geometry can use the available footprint more efficiently |
| Low ceiling | Tank dimensions can be adjusted to reduce overall height |
| Structural columns | Tank geometry can be coordinated with available column spacing |
| Restricted doorway | Sectional fabrication or site assembly may be considered |
| Complex piping | Connection locations can be coordinated with the system |
| High-rise or parkade application | Tank dimensions can be designed around the building layout |
| Retrofit project | The replacement tank can be designed around existing access and equipment |
| Non-standard capacity or dimensions | Fabrication allows project-specific size and geometry |
The goal is not to make every tank custom.
The goal is to avoid redesigning an entire building or mechanical system simply because a standard tank has the wrong dimensions.
Information Your Tank Manufacturer Will Need
You can speed up the initial design review by providing basic project information.
Start with:
Required capacity
How much total and working storage does the project require?
Available dimensions
What maximum length, width, and height are available?
Tank location
Is the tank located in a parkade, mechanical room, basement, rooftop area, industrial facility, or another location?
Stored liquid
Will the tank hold potable water, non-potable water, rainwater, stormwater, wastewater, process water, or another liquid?
Access path
What are the smallest doors, corridors, openings, elevators, or other restrictions between the delivery area and the final tank location?
Connections
Where are the inlet, outlet, overflow, drain, vent, and instrumentation connections expected?
Building and project requirements
Are there seismic, structural, service-access, or other project-specific requirements that need to be considered?
A simple floor plan or sketch can often communicate the problem faster than a long description.
Mark the proposed tank area, surrounding walls, columns, equipment, piping, and major access restrictions.
A Better Way to Approach Tight-Space Water Storage
When a large water or stormwater tank does not fit inside your building, reducing capacity or redesigning the room are not always the only options.
Start by separating three questions:
- How much storage capacity does the project require?
- What physical envelope is actually available?
- How can the tank geometry and installation method connect those two requirements?
That is where custom fabricated plastic tanks can provide an alternative to standard tank configurations.
For projects involving mechanical rooms, basements, parkades, high-rise buildings, retrofits, or other restricted spaces, early coordination can prevent installation problems later in the project.
Have a Tight-Space Tank Project?
If your project requires a large water, rainwater, wastewater, or stormwater tank but available space is limited, BARR Plastics can review the project requirements and available installation envelope.
Send us your room dimensions, equipment layout, plan drawing, or existing tank information.
Our team can review whether a custom fabricated tank may fit the available space and discuss potential tank dimensions, connections, access requirements, and installation considerations.
Request a Custom Tank Design Review
Contact BARR Plastics at 1-800-665-4499 or info@barrplastics.com to discuss your project.