Winter-Proofing an Empty House in Japan: The Job Nobody Tells Overseas Owners About

An empty house in Japan does not sit still over winter. Water expands by about nine percent when it freezes, and a copper or resin pipe full of still water in an unheated house is a pipe that splits.

The cruel part is the timing. Nothing happens on the night it freezes. The split stays plugged with ice until the thaw, and then the house floods — at three in the morning, in February, with the owner eight thousand kilometres away and nobody holding a key.

This guide covers the one maintenance job that matters most for an empty Japanese house, when it is due, and how to get it done when you are not in the country.

At a glance

Question	Short answer
What is the job called?	水抜き (mizunuki) — draining the water out of the plumbing.
When does it need doing?	Before the first hard freeze. Mid-November in Hokkaido; early December in Tohoku, Hokuriku and mountain areas.
What temperature is the trigger?	Sapporo's waterworks uses minus 4°C, or a day that stays below zero, as the signal.
Doesn't closing the water account handle it?	No. Stopping the account stops the billing. The water already inside the house stays there.
What does it cost?	Usually a small call-out for a local plumber, and far less than one burst pipe.
What if the house is in Tokyo or further south?	Lower risk, not zero. Outdoor taps, water heaters and exposed pipework still burst in a cold snap.
Can it be arranged from overseas?	Yes — somebody local has to enter the house, but you do not.

Why an empty house is the dangerous case

A house somebody lives in is defended by ordinary life. The heating runs, taps are used, and a drip or a cold radiator gets noticed the same day.

An empty house has none of that. The building cools to the outside temperature, the water in the pipes has been standing still for months, and nobody is there on the morning the ceiling comes down. A leak that a resident would catch in ten minutes runs for six weeks.

Japanese municipalities in cold regions treat this as a routine seasonal hazard rather than an exotic one. Sapporo City Waterworks runs a public campaign each winter on a single line — minus 4°C is the signal to drain — and warns that freezing is most likely when the outside temperature drops below minus 4°C, when a day stays below zero, and when water has not been used for a long period. An empty house ticks the third box permanently.

The one job: 水抜き (draining)

Houses in cold parts of Japan are built with a drain valve (水抜き栓), usually a handle or a rod in the floor, in a cupboard, or in a box outside. Turning it shuts the supply and lets the water in the indoor pipes run out, so there is nothing left to freeze.

Done properly the job covers:

• The drain valve itself, then opening the taps so the lines empty rather than hold a vacuum.
• The water heater — a tank left full is the single most expensive thing to split.
• The toilet: the cistern and, on many models, the trap, which is usually protected with antifreeze rather than left dry.
• The washing machine hose, the outdoor tap and any garden line.
• The kitchen, basin and bath traps, which need antifreeze if they are to be left for months.

This is a ninety-minute job for somebody who has done it before, and a bad job done in a hurry is worse than none — half-drained pipes still burst.

The trap that catches overseas owners

Many owners close the water account when they leave, and reasonably assume that settles it. It does not. Sapporo's waterworks states the position plainly: when you stop your water service, the utility does not close the stop valve at the meter, and customers are asked to drain the pipes themselves using the drain valve.

Stopping the account stops the bills. It does not empty the house.

When it is due

The deadline is set by where the house is, not by when you happen to be thinking about it.

Region	Do it by	Notes
Hokkaido	Mid-November	Freezing nights can start in October. Do not cut it fine.
Tohoku, Hokuriku, Nagano and mountain areas	Early December	Snow arrives with the cold; access gets harder as the season goes on.
Inland Kanto, Chubu, inland Chugoku	Early December	Sub-zero nights are normal away from the coast.
Tokyo, coastal Kansai, Kyushu, Shikoku	Watch the forecast	Whole-system draining is often unnecessary, but outdoor taps, water heaters and exposed pipes still need protecting.
Okinawa	Not a concern	Damp and typhoons are your winter problem, not ice.

Access is the reason to go early. The plumber who will do this in November for a routine fee is, in January, doing emergency call-outs on burst pipes all day and cannot reach a house up an unploughed road.

What a burst pipe actually costs

The repair to the pipe is the cheap part. What follows is not:

• Water running for weeks. A supply line that splits keeps delivering until somebody notices. The bill lands on the account holder, and utilities are often reluctant to write off consumption that was genuinely delivered.
• The building. Soaked walls, ruined flooring, ceilings down, and then mould through a house that nobody is airing.
• In a condominium, your neighbour's flat. Water finds the floor and keeps going. The unit below loses its ceiling, its lighting and whatever was underneath, and the owner above is liable.
• Your insurance position. Policies commonly cover water damage from a burst pipe, but an insurer looking at an unoccupied, unmaintained house asks harder questions — and an empty house may not be insured the way you assume. See our guide to fire and earthquake insurance for overseas owners.

The rest of the winter list

While somebody is in the house, the same visit should cover:

• Snow on the roof. Wet snow is heavy, and in heavy-snow regions clearing it is a normal part of owning a building. It is also genuinely dangerous work — it kills people in Japan every winter — so it is a job for a contractor, never for a visiting owner on a ladder.
• Gutters and downpipes. Blocked with autumn leaves, they freeze solid and push water back under the roof edge.
• Anything that can blow away. Winter storms on the Sea of Japan side are as strong as typhoons.
• The post box. An overflowing post box tells every passer-by that the house is empty — and the tax notices and municipal letters inside it are the ones you cannot afford to miss.
• A look around inside. Damp, animal entry and a small roof leak are all cheap in November and expensive in April.

There is a legal edge to this as well. Since the 2023 amendment to the Vacant Houses Special Measures Act, a municipality can designate a poorly maintained property as a 管理不全空家, and once a recommendation is issued the residential land discount on fixed asset tax is withdrawn. A house with a collapsing roof and a burst-pipe flood inside is exactly the kind of building that attracts attention — see the risks of leaving a Japanese property unmanaged.

Doing it from overseas

You cannot drain a house from abroad, but you do not need to be there. What has to happen locally is: somebody gets in, does the work, and tells you it is done.

The practical route is:

1. Decide now who holds a key. This is the step that stalls everything else in December.
2. Book before the cold. October and early November for the north; November for everywhere else that needs it.
3. Ask for photographs. A drained system looks like nothing at all, so the record of the visit is what you are paying for.
4. Check the insurance at the same time. Some policies expect a property left empty to be declared.
5. Diarise the re-opening. Water turned back on in a drained house needs somebody present — taps get left open during draining, and an unattended re-opening floods the building just as thoroughly as a freeze.

How Japan YES helps

We arrange this with a company near the property, agree the scope and the quote with you first, and send you the photographs afterwards. The same visit can pick up the snow, the gutters and a general look over the building.

Alongside it we act as your tax representative (納税管理人) and your contact address in Japan, so the water bill, the insurance paperwork and the municipal notices reach somebody who reads Japanese and can act before a deadline passes.

If your property will be empty this winter, tell us where it is and we will tell you what needs doing and by when.