Kagura EstatesJapanese real estate advisory

Due Diligence

Water, Sewer, Gas, Retaining Walls, and Site Infrastructure Checks

Map each service from public network to building and establish ownership, capacity, rights, condition, upgrade cost, drainage, and retaining-wall responsibility before pricing the site.

6 minAdvisory memo

Infrastructure is part of the property, not an afterthought

A land or house listing can state “public water,” “sewer,” or “city gas” while leaving unanswered where the main lies, whether the property is connected, who owns the service line, what capacity exists, whether it crosses private land, and who pays to repair or upgrade it. Retaining walls and drainage can create liabilities larger than visible building work.

Prepare a site-services plan covering potable water, wastewater, stormwater, gas, electricity, communications, private roads, wells, septic systems, pumps, tanks, ditches, culverts, retaining walls, and access for maintenance.

Trace each utility to the public system

Obtain utility maps, meter records, connection applications, pipe sizes and materials where available, inspection and repair history, bills, easements, road-excavation rights, and authority or provider responses. Walk the visible route and identify meters, covers, valves, poles, tanks, drains, and shared facilities.

A public main in the road does not prove a compliant private connection. A functioning tap does not prove adequate capacity for redevelopment or multiple units. Ask the provider about planned use, upgrade, connection charge, lead time, road works, and reinstatement.

Where lines cross neighbouring or shared private land, review passage and excavation rights, repair access, consent, cost sharing, and successor effect. A handshake arrangement with the current neighbour is not durable infrastructure evidence.

Water supply questions

Identify public or private supply, service diameter, pressure, meter ownership, shared pipes, storage tanks, pumps, leaks, water quality, freeze exposure, and upgrade capacity. For a well, obtain rights, depth, pump, testing, treatment, maintenance, drought, contamination, and alternative supply information.

For multi-unit or high-demand use, an existing small line can require replacement from the main. Include design, road occupancy, excavation, traffic control, consent, and reinstatement rather than only the pipe cost.

In a condominium, determine which pipes are common and which serve the unit, planned replacement, past leaks, shut-off procedure, and responsibility under the bylaws.

Wastewater and stormwater are separate

Confirm public sewer connection, private lateral, invert and slope, pumps, shared lines, inspection points, capacity, damage, root intrusion, and backflow. Where a septic system is used, obtain approval, type, capacity, service, testing, desludging, failure history, replacement area, and conversion plans.

Map roof, site, road, slope, and retaining-wall drainage. Determine where rainwater lawfully discharges and whether neighbouring water crosses the site. Inspect during wet conditions where safe. Ponding, damp foundations, blocked channels, or improvised pipes deserve specialist review.

Do not connect stormwater to wastewater or another parcel based on physical convenience without confirming authority and rights.

Gas, electricity, and communications

Identify city gas or LPG, pipe and meter status, appliance capacity, ventilation, tank location, contract, and earthquake shut-off. For electricity, record service capacity, phases, panel, earthing, older wiring, solar or battery systems, poles, underground routes, and upgrade need. Renovation, all-electric conversion, vehicle charging, lifts, pumps, or rental subdivision can materially increase demand.

Confirm fibre or communications route where remote work, security, or property management depends on it. A portal availability result should be verified for the exact address and building entry.

Retaining walls need an ownership and engineering file

Record location, parcel, height, construction, age, approval, inspection, drainage, deformation, cracks, bulging, corrosion, vegetation, loading, and which land is supported. Identify uphill and downhill owners and any agreement. A wall on the neighbour's land can still affect the subject; a wall on the subject can support someone else.

Commission appropriate engineering review for material walls or slopes. Estimate investigation, drainage, repair, replacement, access, temporary support, design, approval, neighbour coordination, and disposal. Standard house inspection may exclude or only visually note the wall.

Check current hazard and slope designations, but do not treat the map as a wall-condition report.

Put upgrade costs into buildable value

For a redevelopment or major renovation, obtain written utility and site-work assumptions before deriving land value. Deduct connection, capacity, consent, road, drainage, wall, demolition, design, authority, and contingency from the residual value. A cheap site can be expensive because the service route and slope are difficult.

For an existing home, identify immediate safety or water issues, near-term replacement, and operating reliability. For a remote owner, add inspection, freeze, storm, pump, tank, and emergency response.

Evidence checklist

  • Provider and authority maps and written responses.
  • Actual connection, route, ownership, diameter or capacity.
  • Passage and excavation rights across private land.
  • Bills, inspections, leaks, repairs, and shared-cost history.
  • Wastewater, septic, stormwater, and backflow evidence.
  • Gas, electrical, communications, tanks, pumps, and meters.
  • Retaining-wall ownership, approval, drainage, and engineering.
  • Upgrade scope, cost, lead time, permits, and reinstatement.
  • Contract allocation for missing rights or seller work.

Worked site-cost example

Consider a sloped house site connected to public water through a 13 mm shared private line, using an older septic system, with city gas available only in the public road and a retaining wall supporting the uphill garden. The buyer plans a larger replacement house.

The diligence budget should include a provider response on required water capacity; route and excavation consent; septic capacity, condition, and sewer-conversion possibility; gas connection and road work; electrical upgrade; wall ownership, approval, drainage, and engineering; and temporary construction access. The existing home's functioning utilities do not prove the replacement can use them.

If these costs and rights remain unresolved, the land residual should carry explicit allowances and a contingency. Treating each listing checkbox as a completed service can overstate buildable value before design begins.

Contract and handover controls

Schedule the services and rights the seller represents, including meter identifiers, shared lines, private agreements, permits, wall or drainage records, and outstanding charges. State any seller work, provider confirmation, consent, testing, or repair required before settlement and the evidence that completes it.

At handover, collect keys to meters, plant and access points; manuals; service contracts; emergency contacts; testing and maintenance records; pump, tank, septic, and treatment schedules; utility bills; and neighbour or shared-facility agreements. Photograph readings and visible condition.

For remote ownership, appoint a responder who can isolate water or gas, manage pump or tank failure, inspect after storms and freezing, and coordinate neighbours or providers. Infrastructure risk becomes more expensive when no one has authority to act.

Primary sources

Reviewed against the linked sources on 23 August 2026. Utility providers, authorities, title documents, and specialist site review control.

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