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Guided estimate
Chapter 2 · Lesson 2.9Underground Water Tank
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01 Days

6,000 L · 10,000 L · 15,000 L

Turn capacity into backup time.

Tank size is easier to understand when you convert litres into how many days of water the house can store.

Tank capacities compared as backup days relative to household water demand
The real question

How much water does the house use each day, and how many backup days do you want?

Compare the capacities

02 Options

The biggest tank is not automatically safest.

Capacity should match occupancy and the reliability of incoming supply.

6,000 L

Lower storage

Takes less underground space and may suit lower occupancy or reliable supply.

Check whether backup is enough.
10,000 L

Middle capacity

More buffer without moving to the largest tank.

Still needs a demand-based reason.
15,000 L

Large storage

Longer backup or larger household capacity.

Needs more space, excavation and cleaning volume.
Smaller can work

Not a quality grade

A small household with reliable supply may need less than 6,000 L. Calculate first.

Plan the tank as maintainable infrastructure

03 Access

Storage must remain inspectable and cleanable.

The capacity number does not describe the inspection cover, overflow, cleaning access or available underground space.

Ask before approval
What daily demand and backup period produced this capacity?
  • Where is the inspection cover?
  • How does overflow discharge safely?
  • Can the tank be emptied and cleaned?
  • What else competes for underground site space?
Calculate backup days

04 Lab

Make the number meaningful.

Change household demand or tank capacity and read the result as backup time.

Backup-day calculator

Working backup10 days

Change either input to complete the demand-based comparison.

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