A cesspool is a sealed underground tank where sewage
is stored until emptied by a tanker vehicle. Building
Regulations require a cesspool serving a residential property
to have a minimum capacity of 18,000 litres (4,000 gallons)
for two users, which should be increased by a further
6,800 litres (1,500 gallons) for each additional user.
Typically, a tank serving a family of four is likely
to need one tanker load removed every two weeks or so,
to prevent it from overflowing. This makes a cesspool
the most expensive option for domestic use and is only
recommended as a last resort.