Water Conservation in an Apartment: What Genuinely Saves Litres

City water use seems trivial individually but adds up enormously at scale. The average apartment household uses 150-200 litres per person per day in most European cities. Most of this is heated, which means saving water also saves energy. The opportunity for meaningful reduction is real.

Here is what genuinely saves significant water in a flat, and what doesn’t.

The four streams of household water

Water use in apartments falls into four main categories:

1. Bathing (shower or bath): 30-40 percent of household water.
2. Toilet flushing: 20-30 percent.
3. Laundry and dishwashing: 15-25 percent.
4. Tap use (cooking, drinking, handwashing): 10-20 percent.

Effective conservation targets the largest streams first. Saving 10 percent of bathing water has dramatically more impact than saving 50 percent of tap water.

Bathing: the single biggest opportunity

A standard showerhead delivers 9-15 litres per minute. A 10-minute shower at 12 LPM uses 120 litres. The fixes:

• Shorten showers. Cutting from 10 to 5 minutes saves 60 litres per shower. Across one shower per day per person, that’s 22,000 litres per year saved per person.
• Install a low-flow showerhead or aerator insert. Cost: £10-25. Reduces flow from 12 LPM to 7-8 LPM without dramatic comfort loss. Renter-friendly: screws onto existing fitting, can be removed at move-out.
• Turn off the shower while soaping/shampooing. Saves 30-40 litres per shower if applied consistently. Requires a more frugal mindset than most people have.
• Take showers instead of baths. A bath uses 80-150 litres; a 5-minute shower at low flow uses 40 litres. Reserve baths for occasions, not daily routine.

Toilet flushing

Older toilets use 9-13 litres per flush. Modern dual-flush toilets use 4 litres for full flush, 2 litres for half flush. The renter-friendly interventions:

• Use the half-flush appropriately. Half-flush is sufficient for liquid waste, full-flush for solid. Many users default to full-flush; the half-flush exists for a reason.
• Cistern displacement device. A sealed water-filled bottle placed in the cistern reduces the water used per flush. £5 for a commercial device, free if you fill a 1L plastic bottle yourself.
• Report leaking toilets. A toilet that runs continuously between flushes wastes 100-200 litres per day. Get the landlord to fix it; it’s their responsibility.

Laundry

A standard washing machine uses 50-60 litres per cycle, regardless of load size:

• Run full loads only. A half-full load uses essentially the same water as a full load. Wait until you have a full load before running.
• Use the eco cycle. Modern machines have an eco mode that uses 20-30 percent less water (and energy) than standard cycles. Takes longer but is much more efficient.
• Skip the pre-wash. Most loads don’t need the pre-wash cycle. Skipping it saves 15-20 litres per load.

Dishwashing

Surprisingly, modern dishwashers use less water than hand-washing for full loads:

• Modern dishwasher (full load, eco cycle): 8-12 litres.
• Hand-washing in a basin: 15-20 litres.
• Hand-washing under running tap: 30-100 litres.

If you have a dishwasher, use it for full loads on the eco cycle. If hand-washing, use a basin rather than running water.

Taps and small leaks

Taps and small leaks add up:

• Aerator on bathroom taps. Reduces tap flow from 6-8 LPM to 3-4 LPM. £5 each, screws into existing thread. Reversible.
• Turn off the tap while brushing teeth, shaving, etc. Saves 6-12 litres per use.
• Fix small drips immediately. A slow drip wastes 5-10 litres per day; a faster one much more. The landlord should fix; report it.
• Rinse vegetables in a bowl, not under running water. Saves 10-20 litres per meal prep.

Hot water double-benefit

Roughly 30-40 percent of household water is heated. Saving heated water saves both water and the energy used to heat it. The hot-water savings are roughly twice as valuable as the cold-water savings.

The implication: prioritise shower-length reduction, hot-tap discipline, and full dishwasher/washing machine loads over interventions targeting cold water.

The grey-water question

Grey water (used water from sinks, showers, washing machines) can in principle be reused for non-drinking purposes (toilet flushing, plant watering). In owner-occupied homes with structural plumbing access this is possible. In rented apartments it’s essentially not.

The only renter-friendly grey-water move: keep a bucket in the shower to catch the cold water that runs while it heats up, and use that for plant watering or toilet flushing. This is a small but real saving.

The rainwater question

Similarly, rainwater harvesting requires structural setup (roof gutters connected to a tank). Not available to most flat-dwellers. The exception: small balcony rainwater collection for plant watering, which works for plant care but isn’t a meaningful overall water saving.

Related: Hot Water Savings in a Shared Flat: Negotiating With Housemates

The bottled water question

Bottled water has zero direct effect on household water consumption (it’s separate from your taps) but has enormous embodied water in its production and transport. The energy and water used to produce bottled water is roughly 3-5 times the water inside the bottle.

The intervention: drink tap water. In most European cities, tap water is safer and tastes similar to bottled. If the local taste is off, a basic water filter (£20-40 for a Brita-style jug) addresses it. The bottled-water habit is one of the most environmentally costly small habits in modern urban life.

Related: Solar Options That Renters Can Actually Use

Measuring your impact

If your flat is metered (most modern flats are), watch the meter for one week. Note the daily consumption. Implement the interventions in this article for a month, then watch again. Most households see a 20-40 percent reduction in metered consumption from these changes.

If your flat is not metered (older flats, some social housing), the interventions still have indirect benefit through reduced hot-water energy use, but the financial feedback loop is missing.

Related: Phantom Load: The Standby Electricity Bill You Didn’t Know You Were Paying

The energy math in one table

Key point	What it means in practice
Bathing (shower or bath)	30-40 percent of household water.
Toilet flushing	20-30 percent.
Laundry and dishwashing	15-25 percent.
Tap use (cooking, drinking, handwashing)	10-20 percent.

The big picture

Water-stressed cities (much of southern Europe, increasingly parts of northern Europe in summer) need every household to think about consumption. Even in water-abundant areas, the energy used to heat water makes saving water an indirect carbon win.

The most impactful interventions are also the cheapest and most reversible. A £25 investment in a low-flow showerhead insert and tap aerators, plus a few habit changes around shower length and full appliance loads, can reduce household water use by 30-40 percent. The payback is immediate on metered properties and beneficial on energy bills regardless.

Sources and further reading

• Energy Saving Trust
• World Resources Institute: Aqueduct