Estimate the water entering a sump from a rectangular display’s surface drop and one cylindrical return-pipe section. Compare the total with the sump’s measured available capacity. This is a geometry estimate: it does not predict where a siphon breaks, how valves behave, or whether your aquarium will overflow.
Enter internal display length, internal width, surface drop, pipe internal diameter and draining pipe length in centimetres. Enter measured free sump capacity in litres. For example, enter 120 for a 120 cm display and 2.5 for a 25 mm pipe bore.
Surface drop means the difference between the running display water level and the level where drainage actually stops. Establish this from your actual plumbing and siphon behaviour; the calculator cannot determine it. Pipe length means the water-filled length whose contents enter the sump, measured along the pipe. Use the internal bore, not the nominal pipe size or outside diameter. The pipe term represents its initial water inventory and must not duplicate water already included in another allowance.
Free sump capacity is the additional water the sump can accept from its normal running level to your chosen maximum level, allowing for equipment, baffles and inaccessible space. It is not the sump’s advertised total volume. Any reserve you want to retain must already be excluded from this input.
This calculator performs scalar arithmetic on numerical measurements: registered unit 1 represents each measurement divided by its stated reference unit, such as length divided by 1 cm or capacity divided by 1 litre. Labels specify those reference units; there is no automatic unit conversion. The two fixed numerical factors must remain unchanged.
The display term uses the rectangular-box formula, length × width × height. Wolfram MathWorld: Volume.
The pipe term uses the cylinder formula, one-quarter × π × diameter² × length. Wolfram Formula Repository: Cylinder Volume.
Adding these two volumes and subtracting their total from available sump capacity is the calculator’s geometric model. These formula references do not establish your aquarium’s drainage behaviour.
- Positive: the modelled drain-down fits within the capacity entered, leaving that many litres. This does not certify the installation against overflow.
- Zero: the model uses all entered capacity, leaving no remaining allowance.
- Negative: estimated drain-down exceeds entered capacity; the magnitude is the modelled shortfall in litres.
Displayed results are rounded to three decimal places. A displayed zero may conceal a very small positive or negative result; measurement uncertainty matters more than this display precision. An unavailable result is not zero and must not be interpreted as adequate capacity.
| Case | Display L × W × drop (cm) | Pipe bore × draining length (cm) | Available capacity (L) | Display volume (L) | Pipe volume (L) | Total drain-down (L) | Headroom (L) |
|---|---|---|---|---|---|---|---|
| Default example | 120 × 50 × 2 | 2.5 × 200 | 20 | 12.000 | 0.982 | 12.982 | 7.018 |
| Capacity shortfall | 120 × 50 × 2 | 2.5 × 200 | 10 | 12.000 | 0.982 | 12.982 | -2.982 |
| No pipe inventory included | 100 × 40 × 1.5 | 2.5 × 0 | 6 | 6.000 | 0.000 | 6.000 | 0.000 |
For the default example, display drainage is 120 × 50 × 2 ÷ 1000 = 12 L. Pipe drainage is π × 2.5² × 200 ÷ 4000 ≈ 0.981748 L. Total drainage is approximately 12.981748 L, leaving 20 − 12.981748 ≈ 7.018252 L. Calculations retain intermediate precision; only displayed results are rounded.
Supported entry bounds are 0.1–1000 cm for each display dimension, 0–200 cm for surface drop, 0.1–30 cm for pipe bore, 0–10000 cm for draining pipe length and 0–100000 L for available capacity. These are calculator entry limits, not recommended aquarium dimensions. Surface drop must also be physically possible for your display. A zero pipe length omits its inventory; a zero surface drop omits display drainage.
The model assumes a rectangular display with constant horizontal area and a single uniform cylindrical pipe section whose included contents drain into the sump. It does not independently include overflow boxes, drain lines, other return branches, fittings with additional volume, connected vessels, automatic top-up water or transient surges. Account for these separately before relying on the comparison. A non-rectangular display or varying pipe bore needs a suitable separate volume calculation.
Check actual plumbing and siphon behaviour during a controlled pump-off test with enough spare capacity and a way to stop the test before overflow. Confirm the final display level, the volume entering the sump and the highest sump level. Do not assume a check valve or siphon-break opening guarantees a particular stopping level. Recheck after changes to outlets, plumbing or operating water levels. The calculator neither simulates flow nor supplies a universal safety margin.
A registered thumbnail has not been supplied for this proposal. Create and register a 400 × 400 pixel WebP thumbnail before activation, then insert it as the first image block using its real asset ID. Brief: a cheerful yellow five-point star mascot with hands, floating without separate legs or feet, beside a simplified aquarium and sump with a marked water-level drop; white background and playful navy, blue and teal educational graphics. Inspect neighbouring registered thumbnails for style consistency. No asset ID or image path is invented here.