Slurry Tank Capacity Calculator

Work out the usable capacity of your slurry tanks and lagoons after freeboard and winter rainfall.

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Rules for

1. Your slurry stores

0.0 m³ usable

2. Storage period and rainfall

Rainfall: 25 mm a week = 550 mm.

From the storage required calculator.

Capacity

Total volume

0

m³

Less freeboard

0

m³

Less rainfall

0

m³

Usable for slurry

0

m³ · 0 gallons

Volumes are calculated from the dimensions you enter and don’t allow for crust, sludge build-up or internal walls and pillars. For an exact figure, use the design drawings.

Working out usable slurry capacity

The capacity that counts is not the full volume of the tank. You must leave freeboard — 300 mm in concrete and steel tanks and 750 mm in earth-banked lagoons — and rain falling into any uncovered store over the winter uses up space too.

This calculator takes the dimensions of each store, removes the freeboard and the rainfall for the storage period, and gives the usable volume in cubic metres and gallons. Compare it with the figure from the slurry storage required calculator to see whether you have enough.

In Northern Ireland, slurry tanks built, enlarged or reconstructed after 31 December 2019 must be covered, and new above-ground tanks must be at least 50 m from a waterway.

Frequently asked questions

What freeboard do slurry stores need?

300 mm for concrete and steel tanks and 750 mm for earth-banked lagoons. The store must not be filled above that level. The rules are the same in Northern Ireland (NAP Regulations Schedule 6) and England (SSAFO Regulations).

Why take rainfall off the capacity?

Rain falling into an uncovered store over the winter takes up space that would otherwise hold slurry. DAERA uses 25 mm a week as the Northern Ireland winter average — about 550 mm over 22 weeks. Covering a tank keeps that space for slurry.

How do I measure an irregular lagoon?

Choose “I know the volume” and enter the volume up to the freeboard level from the design drawings, plus the open surface area so rainfall can be allowed for. For sloped-sided lagoons, measure the average of the top and bottom dimensions.

How many gallons is a cubic metre?

One cubic metre is about 220 UK gallons (219.97). A 1,000 m³ tank holds roughly 220,000 gallons.

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