A tank can still contain water after its normal withdrawal system has reached its usable limit. That physical reality matters for a society managing water supply, but it does not mean the monitoring dashboard must misrepresent what is available.
TownEve allows the tank dimensions and dead-water height to be entered during dashboard setup. The usable range can therefore be reflected in the displayed calculation.
For example, if the bottom 10% of the tank's physical storage is unusable under the configured operating arrangement, that water can be excluded from the available-water calculation. At the defined dead-water level, the dashboard shows 0% usable water rather than presenting that residual physical water as available supply.
This is an important distinction between merely observing a water surface and configuring a monitoring system around how a particular tank is actually used.
Physical storage and usable storage
A tank's nominal or geometric capacity describes its physical storage volume. The amount of water currently present depends on the water level and the tank geometry.
Usable storage describes the portion above the configured dead-water limit. It is the relevant quantity when the operating question is how much water remains available for the intended withdrawal arrangement.
These quantities can differ without either measurement being wrong.
A sensor can observe the water surface while the dashboard applies the configured dimensions and dead-water reference to calculate the usable percentage.
Why dead water exists
A tank may have a withdrawal point or suction arrangement above its physical bottom. Under that operating arrangement, water below the relevant level may not be available through the normal supply path.
The exact unusable height is specific to the tank and its installed plumbing. It should not be assumed to be 10% everywhere.
The site team needs to establish the relevant dead-water height using the verified as-installed arrangement and its operating requirements.
TownEve's tank-specific configuration accommodates that site-specific input, allowing the usable-water calculation to reflect the verified operating reference for each monitored tank.
How the dashboard calculation works
During setup, the tank's dimensions are entered, along with the dead-water height where applicable.
The configured usable range starts above the dead-water limit. Once the water surface reaches that configured limit, the available-water display can read 0%, even though some physical water remains below it.
For a simple illustrative tank, imagine a total physical storage volume of 10,000 litres and a verified unusable volume of 1,000 litres. The configured usable capacity is then 9,000 litres.
If the tank physically contains 1,000 litres, the usable amount is zero under that definition. If it physically contains 5,500 litres, the usable amount is 4,500 litres, or 50% of the configured 9,000-litre usable capacity.
These figures illustrate the calculation, not a standard tank shape or a claim that dead water is always 10%. For a real installation, the level-to-volume relationship must reflect the entered dimensions and relevant geometry.
Why a raw percentage can mislead
A raw geometric percentage that counts every litre below the surface may be a poor indicator of available supply if it includes inaccessible water.
A tank showing 10% of its physical volume could already be at its usable minimum in the example above.
TownEve's dead-water configuration addresses that distinction by making the available-water calculation reflect the tank's operating reference.
The facility team should still know how its particular dashboard has been configured and which quantity each display represents.
Dead-water height must be established correctly
The calculation is only as useful as its setup inputs.
The society should verify the tank dimensions, the relevant withdrawal arrangement and the dead-water height with the qualified site team. A nominal drawing may not capture every as-installed detail.
If the withdrawal arrangement changes, the configuration may need review.
Do not choose a dead-water height by guesswork, and do not run pumps into unsafe conditions merely to discover the lowest operating level.
Tank shape and compartments matter
A vertical height does not always correspond to the same fraction of volume in every tank shape.
The configured dimensions and applicable geometry determine how a measured level translates into stored or usable volume.
Where a structure has separate compartments or different withdrawal points, the usable reference may differ between them. The site team should establish the correct mapping rather than treating hydraulically separate storage as one undifferentiated tank.
TownEve's configuration should be set up for the actual monitored asset and its intended service.
Setting low-water alerts against usable storage
Once the usable range is configured, the society can choose alert thresholds with a more meaningful understanding of available storage.
An alert intended to give the facility team time to investigate a supply interruption should generally be set above the operational zero, according to the site's verified response requirements.
TownEve currently supports configured email alerts. The threshold and the responsible recipients should be agreed during setup and acceptance.
An informational alert is not the same as an engineered pump-protection interlock. Equipment protection must be designed separately where required.
Usable storage is not a promise of tap pressure
Excluding dead water makes the storage calculation more relevant to the property's operating arrangement. It does not turn a tank-level sensor into a direct measurement of water pressure or distribution performance.
A pump failure, closed valve or other distribution issue may interrupt service even when the dashboard shows usable water in storage.
The dashboard answers the storage question. The facility team still needs the appropriate equipment and distribution information to diagnose delivery problems.
Can the display guarantee remaining supply hours?
No. A configured usable percentage gives a better-defined storage reference, but the duration of supply depends on changing demand and replenishment.
A percentage should not be converted into a guaranteed number of hours without suitable assumptions and validated additional information.
The value of the usable-water calculation is that it avoids counting the configured dead-water portion as available, not that it predicts every future operating condition.
A practical commissioning check
Confirm the dimensions entered for the monitored tank and document the dead-water height and how it was established.
Check that the dashboard's zero-usable reference matches the agreed operating limit. Verify representative displayed values against the configured geometry and appropriate independent observations.
Record the tank identity, relevant service, calculation convention and alert thresholds so future facility teams understand what the percentage means.
If the physical arrangement or setup changes, review the configuration rather than assuming the original reference remains correct.
What residents should understand
A resident-facing percentage should have a clear meaning.
When TownEve is configured to exclude dead water, the displayed usable percentage is not merely the fraction of the tank's physical volume that contains water. It is calculated against the configured available range.
This is helpful during a shortage because it avoids presenting inaccessible residual water as though it were usable supply.
Operational notices should still distinguish verified storage conditions from the actual status of distribution to residents.
Where TownEve fits
TownEve combines contactless ultrasonic tank-level monitoring with configurable tank dimensions and dead-water height.
That allows the dashboard calculation to exclude the configured unusable portion and represent available storage more meaningfully for the site's withdrawal arrangement.
The product also provides current and historical levels, configured email alerts and telemetry-freshness monitoring.
This is a strength of TownEve's site-specific setup: tank dimensions and dead-water height logged in the dashboard allow the usable-water calculation to reflect the configured tank geometry, regardless of the tank's size or shape. Accurate results still require correct inputs and a valid level reading; this does not replace pump protection or pressure measurement.
FAQ
If the bottom 10% of a tank is unusable, will TownEve still show 10% available?
Not when the dead-water height is correctly configured. The available-water calculation can show 0% at that defined limit.
Does every tank have 10% dead water?
No. The relevant height depends on the actual tank and withdrawal arrangement.
Can TownEve use tank dimensions in the calculation?
Yes. Tank dimensions can be entered during dashboard setup.
Does a 0% usable reading mean the tank is physically dry?
No. It means the water has reached the configured usable minimum; residual physical water may remain.
Can the usable percentage guarantee water at every tap?
No. Distribution equipment and operating conditions remain separate.
Should the dead-water configuration be checked after plumbing changes?
Yes. A changed withdrawal arrangement may change the appropriate operating reference.
Can a low-level email alert act as automatic pump protection?
No. Informational monitoring and engineered protective controls are separate.
Related calculation and planning guides
Start with the tank volume calculation for stored-water geometry, then use the resulting usable capacity as an input to housing society water budgeting.