Your loft tank and hot water cylinder: should the tank be covered, and can you drink from them?

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Yes, a loft cold water tank should have a tightly fitting, secured lid, says the Drinking Water Inspectorate. Drink from a mains-fed tap, usually the kitchen cold tap. If you run out of safe water in an emergency, official UK advice says water from hot taps can be drunk once you filter it and then boil it or use purification tablets.

Do this now

1. Find out which taps are on the mains. Do the thumb test below.
2. Look in the loft (safely). Check the tank has a lid that fits and is fastened down.
3. Check the tank is insulated, with a jacket, and the pipes are lagged.
4. Find your stop tap and make sure it turns.
5. Keep some bottled water anyway: 3 litres per person per day for 3 days (GOV.UK Be Ready).

How water reaches your taps

Many UK homes, especially older ones, have two kinds of water:

• Mains water, which comes straight from the water company's pipe.
• Stored water, held in a cold water tank, often in the loft. In many homes this tank also feeds a hot water cylinder.

The DWI says in older homes the kitchen cold tap may be the only tap connected straight to the mains. In some homes, every cold tap is fed from the tank. Newer homes, especially those with unvented heating systems, usually have mains-pressure hot and cold taps.

The thumb test. The DWI says open the tap fully and hold back the water with your thumb. If the flow is weak and easy to hold back, the tap is probably connected to a tank, not the mains.

Should the loft tank be covered?

Yes. The DWI says a cold water tank should have:

• A tightly fitting, securely fastened lid, to keep out light, birds, vermin and dust
• Screens on the vents and overflow, against insects and particles
• Insulation, and no direct sunlight or nearby heat, so the water stays cool
• A sensible size: the DWI says 250 litres is quite enough for most homes, so the water is replaced often

The DWI lists missing lids and warm water as signs that tank water may be getting worse. It says old galvanised iron tanks rust, while modern polyethylene tanks are fine if designed for drinking water. Look for the Water Regs UK Approved Product logo.

It suggests checking a drinking water tank once a year, both the tank and the water. A WaterSafe registered plumber can do this. The owner of the building is responsible for the plumbing. If you rent, the DWI says ask your landlord or agent whether your water comes from a tank, and for any inspection records.

CCW, the water consumer body, also says protect tanks, cisterns and boilers with insulating jackets and lag exposed pipes before winter. See frozen and burst pipes.

Can you drink from the loft tank?

The DWI says tank water will be safe to use if the tank is properly designed, correctly installed and kept in good condition. But it recommends a mains tap for drinking, preparing food and cleaning your teeth wherever possible. It also says cold water from bathroom taps is not recommended for drinking, because it may come from a tank not suitable for drinking water.

So day to day: drink from the kitchen cold tap.

Can you drink from the hot water cylinder in an emergency?

Not straight from the tap. The DWI says hot tap water is not recommended for drinking, partly because it can carry more metals, such as copper.

But in an emergency, the advice changes. The UK Chief Medical Officers' public health scripts for a national power outage say that if you've run out of safe fluids, there are other sources you can drink once you take extra steps to make them safer. They name water from hot water taps.

The extra steps in those scripts are:

1. Use a clean container. Never one that held chemicals such as fuel or paint.
2. Don't drink water with an oily film on top.
3. Filter it through a coffee filter, pillowcase or sheet until it runs clear.
4. Then boil it, or use in-date water purification tablets, following the label.
5. Store the treated water in a cool, dark place.

The same scripts say that while your cold tap is still flowing normally, it is safe to drink. Use that first. Our guide to making water safe when the taps stop covers each method.

Boiling. The DWI's boil water advice says bring the water to a rolling boil, let it cool on its own, keep it in a clean container in the fridge, and throw it away if it isn't used within 24 hours.

Save what's in the tanks

GOV.UK Be Ready says that during a water outage, keeping water use to a minimum makes alternative sources, such as water tanks, last longer. It also says bottled water is the safest option, and that people on their water company's Priority Services Register will have alternative supplies arranged for them. See no water from the tap: what to do.

If a pipe bursts

CCW says turn off your water at the stop tap and switch off your immersion heater, if you have one, and the central heating. See how to turn off gas, electricity and water.

Bottled water is still the plan

The tank and cylinder are a backup, not a store. Be Ready asks for 3 litres of drinking water per person per day for 3 days, plus extra for babies, medical devices and pets. For how to store it, see water storage containers: size, where and how long.

Related guides

• Emergency water at home: how much to store and how
• No water supply: what to do, and what you're entitled to
• Frozen and burst pipes: what to do, and how to prevent them
• How to turn off your gas, electricity and water
• Boil water notice: what it means and what to do

We're an independent UK site, not the government. We check guides against official sources and link to them. In an emergency call 999.

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