Attic Water Tanks for Toilet Backup
Ever seen an attic water tank for toilets? Learn how gravity-fed tanks work, why they’re used in Ireland, and their pros and cons for backup water.
Some homes, especially in parts of Europe, use attic water tanks as a backup supply. While this may look unusual to those used to direct municipal water, it provides an important function during outages.
In Galway, Ireland, one home had a large attic water tank, about 75–100 gallons in size. The tank was mostly open and had a float valve, similar to what you find in a standard toilet cistern. This tank supplied only the toilets in the house.
The purpose of the setup was simple: when city water cuts out, the attic tank provides gravity-fed flushing water for three to five days. The toilets appear normal, but draw water from the tank when the municipal supply stops. This ensures basic sanitation even when water service is unreliable.
Question:
Why do some homes use attic water tanks just for toilets, and how do they work?
Answer:
Attic tanks act as emergency storage. When the municipal supply stops, the tank releases water by gravity to the toilets. A float valve refills the tank when city water returns. This ensures toilets can flush even during outages. These tanks are common in older plumbing systems in Ireland and the UK. However, they are usually not used for drinking or bathing water due to contamination risks.
Homeowners with such systems often buy bottled water for drinking and limit bathing when outages occur. Modern plumbing in some areas replaces these tanks with direct mains-fed systems and pressure boosters, but attic tanks remain practical for backup flushing.
For more insight, see this Irish Water guide on storage tanks. You can also learn more from this Family Handyman article on water storage.
I’m Chris Mayer, writing for Plumbing 101.
