Build a hotel on land the public sewer does not reach, and you treat your own wastewater in an on-site combined treatment tank (johkasou). According to the end-of-FY2025 figures jointly released on August 24, 2026 by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), the Ministry of Agriculture, Forestry and Fisheries and the Ministry of the Environment, Japan’s wastewater treatment coverage rate stood at 94.0%, split into public sewers 82.2%, johkasou 9.5% and rural community sewerage 2.2%. Among municipalities with fewer than 50,000 residents, however, coverage is only 85.1% — and most resort areas fall into that tier. This article checks the JIS A 3302 formula that sizes a johkasou and the maintenance duties under the Johkasou Act against primary sources, puts coverage, lodging supply and estimated settled ADR for 12 resort municipalities from Kutchan to Ishigaki into a single table, and converts installation and annual holding costs for 30-room and 100-room model hotels into per-room and per-occupied-room-night figures.

Executive Summary — A 30-Room Hotel Needs a 113 PE Johkasou Costing ¥13M–¥18M

The conclusions first. One: for a 30-room hotel with 1,500㎡ of floor area and no banquet hall, the wastewater infrastructure cost borne outside a sewer district is estimated at ¥13M–¥18M to install (¥430k–¥600k per room) and ¥630k–¥990k a year to maintain (¥21k–¥33k per room). Per occupied room-night, at an assumed year-round occupancy of 60%, that comes to ¥162–¥242 even including depreciation — around 1% of revenue in resort municipalities where room rates sit near ¥20,000. Two: the biggest swing factor is whether the hotel has a wedding or banquet hall. The JIS A 3302 coefficient doubles from 0.075 to 0.15, so capacity and cost double too. Three: coverage across the 12 resort municipalities ranges widely, from 98.6% in Hakuba to 35.3% in Higashiizu; “resort” does not imply the same wastewater baseline. Four: MLIT’s notice of July 3, 2026 changed how design capacity is handled for detached houses (excluding apartment buildings) and does not affect the formula for hotels and ryokan.

Inside the National 94.0% — Sewers 82.2%, Johkasou 9.5%, and a 15-Point Gap by City Size

According to MLIT’s press release (August 24, 2026), 116.02 million people nationwide were served by wastewater treatment facilities at the end of FY2025, for a coverage rate of 94.0%, up 0.3 points from 93.7% a year earlier. By facility type, public sewers served 101.41 million (82.2% of total population), rural community sewerage 2.76 million (2.2%), johkasou 11.71 million (9.5%) and community plants 0.14 million (0.1%), leaving about 7.4 million people without access to wastewater treatment. That is the national average; for hotel site selection, what matters is the distribution, not the average.

The appendix breakdown by city size (Exhibit 1-1) shows coverage of 99.8% in cities of 1 million or more, 96.5% at 500,000–1 million, 95.6% at 300,000–500,000, 94.1% at 100,000–300,000, 90.6% at 50,000–100,000 and 85.1% below 50,000. Of 1,719 municipalities, 1,232 are in the under-50,000 tier, which is where most resort areas sit. In other words, “where does the wastewater go?” — a question urban developers rarely have to think about — surfaces at the very start of planning in rural resort locations.

The weight of johkasou also varies by prefecture. Taking the seven prefectures that contain our 12 municipalities from the prefectural table (Exhibit 1-3), the share of population served by johkasou is 24.6% in Oita, 19.4% in Shizuoka, 15.3% in Kumamoto, 11.4% in Okinawa, 5.7% in Nagano, 3.3% in Hokkaido and 1.3% in Kanagawa. In Oita, Shizuoka and Kumamoto, “no sewer means johkasou” is an everyday choice prefecture-wide, which suggests a deep bench of licensed contractors for inspection and desludging. Even in Hokkaido and Kanagawa, where sewers serve over 90%, some towns — Niseko and Hakone, as shown below — drop to around 80% and around 70% coverage.

Coverage and Lodging Supply in 12 Resort Municipalities — Hakuba 98.6%, Higashiizu 35.3%

From MLIT’s appendix (Exhibit 1-4, “Wastewater Treatment Coverage by Municipality”), we selected 12 municipalities representing ski, onsen and island resorts and lined up the number of operating lodging properties and rooms tracked by MetroEngines Research with the 12-month median estimated settled ADR. Coverage combines sewers, johkasou and rural community sewerage; because the appendix does not break it down by facility type at the municipal level, the prefectural figures in the previous section fill that gap.

Hakuba tops the list at 98.6%: despite having the most properties of the 12 (319 properties, 4,287 rooms), almost the entire village is served by wastewater treatment. Kutchan (90.6%) and Onna (90.2%) are also above 90%, while Niseko (82.0%), Karuizawa (88.6%), Yufu (84.6%) and Minamioguni (84.5%) sit in the 80s. In contrast, Hakone is at only 71.3%; Aso (68.4%), Ishigaki (66.0%) and Ito (63.2%) fall below 70%, and Higashiizu is at just 35.3%. The room-weighted average for the 12 municipalities is 76.9%, 17 points below the national 94.0%.

Overlaying room rates, there is no simple correlation between coverage and price. Minamioguni (Kurokawa Onsen) has 84.5% coverage and the highest median estimated settled ADR of the 12 at ¥30,700; Hakone is at 71.3% and ¥26,800; Higashiizu, even at 35.3%, posts ¥20,800. Wastewater infrastructure is a cost-side premise rather than a revenue-side constraint: the lower a municipality’s coverage, the more a business plan that assumes “the sewer will never come” becomes the norm. Note that Niseko’s estimated settled ADR rests on only 7–10 properties a month and should be read as indicative.

Hotels Outside Zoning Districts — 66.8% of Properties and 59.5% of Rooms in the 12 Municipalities

Sewer service areas are confirmed site by site in each municipality’s sewer register; no uniform nationwide open data exists. As a reference indicator rather than a proxy, we therefore used the zoning-district data in MLIT’s Real Estate Information Library (zoning polygons under the City Planning Act) and tested whether the coordinates of each of the 1,745 operating lodging properties fall inside or outside a zoning district. Zoning districts are designated for urbanization promotion areas and the built-up parts of non-delineated areas; outside them lie areas beyond city planning areas and the undesignated “white land” of non-delineated areas. Because sewer networks are normally built out from inside zoning districts, municipalities with more hotels outside zoning districts can be read as having more hotels planned around johkasou. That said, some zoned areas still lack sewers, and some unzoned areas are served by specified environmental conservation sewers or rural community sewerage, so the two must not be equated.

The results are polarized. In six municipalities — Niseko, Hakuba, Aso, Onna, Minamioguni and Higashiizu — every operating lodging property stands at a point with no zoning designation. Kutchan is at 96.6% and Ito at 79.9%. Conversely, Karuizawa is at only 10.0% and Hakone at 11.9%, with Yufu (31.0%) and Ishigaki (55.2%) in between. Across the 12 municipalities, 1,165 of 1,745 properties (66.8%) and 21,690 of 36,457 rooms (59.5%) are outside zoning districts. The room-based share is lower than the property-based share because larger hotels tend to sit on the built-up side. This two-layer pattern — properties outside the built-up area, rooms inside it — holds for 2026 openings too; development permits and time-to-opening by city-planning zone are covered in 61% of 2026 Hotel Openings Fall Outside Urbanization Promotion Areas.

These results also intersect with coverage. Hakuba has 100% of hotels outside zoning districts yet 98.6% coverage, suggesting the whole village has been served by public sewers and rural community sewerage. Onna is likewise 100% outside zoning with 90.2% coverage. Higashiizu, by contrast, is 100% outside zoning with 35.3% coverage — a picture in which most seaside onsen inns treat their wastewater with johkasou. The implication for developers is clear: on sites outside zoning districts, check the sewer register for service-area status before applying for building confirmation, and if the site is outside, put johkasou capacity and cost into the business plan at the earliest stage.

The JIS A 3302 Formula — Hotels and Ryokan: Floor Area × 0.075, or × 0.15 With a Banquet Hall

Johkasou size (design capacity) is set by JIS A 3302, “Calculation standard of the population equivalent for septic tanks by building use,” which is cited by Ministry of Construction Notification No. 3184 (1969) under the Building Standards Act. The lodging-related formulas in the version MLIT publishes are shown below; JIS A 3302:2000, cited by sources such as Tokushima Prefecture’s johkasou handling guidelines, uses the same coefficients for hotels and ryokan.

Applying the formula at hotel scale: a 30-room property with 1,500㎡ of floor area and no banquet hall needs 0.075 × 1,500 = 112.5, rounded up to 113 PE. With a banquet hall it is 0.15 × 1,500 = 225 PE — double, for the same room count. At 5,000㎡ and 100 rooms, the figures are 375 PE and 750 PE. A motel is rooms × 5, and simple lodging designed by capacity — such as glamping or campground cabins — uses the capacity itself, so 10 cabins of 4 guests each need 40 PE, which usually comes out smaller than the hotel/ryokan floor-area formula.

The JIS includes a proviso that “where the table clearly does not reflect actual conditions given how the building is used, the calculated population may be increased or decreased,” and when a building has two or more uses, the populations for each use are added together. Hotels with a restaurant or day-use onsen will see additions. In practice, the approach of the designated administrative agency or designated building confirmation body governs (Tokushima Prefecture’s guidelines, for example, apply n = 0.1A to city, business and resort hotels accommodating 50 or more people even without a banquet hall), so the design shortcut is to consult them early, once the floor area is fixed.

MLIT’s Notice of July 3, 2026 — Detached Houses Only; Nothing Changes for Hotels and Ryokan

In a notice dated July 3, 2026 (Kokujushi No. 191 / Kokujusanken No. 2414, “On the Calculation Method for the Design Capacity of Septic Tanks”), the Director of the Building Guidance Division and the Counsellor of MLIT’s Housing Bureau abolished Ministry of Construction Notice Jushihatsu No. 167 of March 31, 1998 (the 1998 notice) and set out new handling. The text of the notice confirms that it applies only to septic tanks for “houses (excluding apartment buildings).” It keeps the existing practice that, where the average number of residents in houses of similar size in the area is below the JIS table’s design capacity, the average of the two may be used as the design capacity, and — on the grounds that changes in household structure and lifestyles may push water use below past assumptions — newly permits johkasou with a design capacity of fewer than 5 persons.

The formulas for hotels, ryokan and simple lodging are therefore unchanged, and this article’s model estimates stand on the JIS formulas as they are. Where hotel developers do face a practical change is in converting existing houses into whole-house rentals or minpaku: whether a sub-5-PE johkasou designed for a house can be used for lodging depends on whether the change of use triggers recalculation under the JIS lodging formulas. That is up to each designated administrative agency, so conversion projects need prior consultation.

Owner Duties Under the Johkasou Act — Article 7 and 11 Inspections, Maintenance, Desludging and an Effluent Limit of BOD 20 mg/L

A hotel that installs a johkasou becomes its “johkasou administrator” and bears maintenance duties under the Johkasou Act. We confirmed the key points against primary sources and official municipal guidance.

Hotel johkasou often exceed 100 PE and use contact aeration or activated sludge. Because inspection frequency depends on treatment method and ancillary equipment rather than capacity, mid-to-large tanks with a flow equalization tank require an inspection contract of at least every two weeks, and activated sludge systems at least weekly. Desludging is at least once a year, but sludge volume rises with guest numbers, so extra desludging after peak season is not unusual. Statutory inspection fees stay at around ¥20,000 a year, while outsourced maintenance and desludging make up most of annual upkeep.

Installation Cost at Scale — MOE’s Published Unit Costs Stop at 50 PE, Falling From ¥167k to ¥115k per Person

The public benchmark for installation cost is the “johkasou installation cost” table that the Ministry of the Environment provides as base parameters for its wastewater treatment cost-comparison software. The standard type costs ¥837k for 5 PE, ¥1.043M for 6–7 PE, ¥1.375M for 8–10 PE, ¥2.039M for 10–15 PE, ¥2.786M for 16–20 PE, ¥3.332M for 21–25 PE, ¥4.066M for 26–30 PE, ¥4.521M for 31–40 PE and ¥5.737M for 41–50 PE; the BOD-removal type costs ¥7.977M for 41–50 PE. Per person, cost falls from ¥167k at 5 PE to ¥115k at 50 PE, reflecting economies of scale. Under MOE’s national subsidy rules, the standard amount for 51 PE and above is set by individual consultation (using the form in the grant guidelines), so the uniform nationwide unit costs end at 50 PE.

Since no published unit costs exist for the 100–750 PE range hotels need, our model holds the 41–50 PE per-person unit cost constant (¥115k for the standard type, ¥160k for the BOD-removal type) and extends it. If economies of scale continue, actual unit costs will come in lower; site conditions such as access roads, ground and securing a discharge point will push them higher. The figures below are therefore “reference ranges extending published unit costs” and are no substitute for quotes. Annual maintenance follows the same logic: we used the 31–40 PE maintenance unit cost of ¥223,300–¥271,920 (covering statutory inspection, maintenance, desludging and repairs, but excluding electricity for blowers etc.) from Towada City’s VFM study for its public johkasou program (November 2021), converted to ¥5,600–¥8,800 per person. This is consistent with Bungo-Ono City’s fee for municipally installed johkasou of ¥128,280 a year for 21 PE (about ¥6,100 per person).

Model Estimates — 30 and 100 Rooms, With and Without a Banquet Hall: ¥162 to ¥483 per Room-Night

For two hotels — 30 rooms on 1,500㎡ and 100 rooms on 5,000㎡ — we calculated design capacity for four cases, with and without a banquet hall, and converted installation and annual maintenance costs into per-room and per-occupied-room-night figures. The room-night conversion assumes year-round occupancy of 60%, an assumption used for the estimate only. Depreciation uses 30 years for the johkasou structure, the reference life given in MLIT’s prefectural planning manual; interest is not included.

Reading the results: for 30 rooms without a banquet hall, an installation cost of ¥13M–¥18M is ¥430k–¥600k per room — 1.4–4.0% of total investment (2–3% around the middle of the combinations) for a hotel whose construction cost falls in the ¥15M–¥30M-per-room band. Annual maintenance of ¥630k–¥990k converts to ¥96–¥151 per room-night, or ¥162–¥242 including 30-year depreciation. In municipalities where estimated settled ADR is around ¥20,000, that is about 1% of revenue: not enough to make or break a business plan, but the kind of cost that forces design changes and refinancing if it is not in the plan from the start.

The per-room figures do not change at 100 rooms only because this article extends a constant per-person unit cost; in reality, economies of scale leave room for the 100-room case to come in lower. A banquet hall, on the other hand, doubles capacity and doubles the per-room-night cost to ¥322–¥483. Whether to include a wedding or banquet hall affects wastewater infrastructure cost more than room count or floor area does, and options such as sharing banquet functions with an existing building on a separate site make sense on this cost line. For operators acquiring and reopening dormant ryokan, the same logic applies directly: check whether the existing johkasou’s capacity fits the current plan, and whether closing a banquet hall frees up calculated headroom.

Sensitivity Analysis — Moving Occupancy and Unit Cost Still Yields ¥107–¥405 per Room-Night

The midpoint values in Table 4 depend on two assumptions: an installation cost extended from published unit costs, and 60% year-round occupancy. For the 30-room, no-banquet-hall, 113 PE case, we therefore calculated the per-room-night cost with unit costs 30% lower (economies of scale) or 30% higher (site conditions), and with year-round occupancy ranging from 40% to 80%. The optimistic scenario (unit cost −30%, maintenance at the low end, 70% occupancy) gives ¥122 per room-night and the pessimistic scenario (unit cost +30%, BOD-removal type, maintenance at the high end, 45% occupancy) gives ¥360 — between 0.6% and 1.8% of a ¥20,000 estimated settled ADR.

On two axes, even the harshest combination (40% occupancy, unit cost × 1.3, BOD-removal type, maintenance at the high end) gives ¥405 per room-night, or 2.0% of a ¥20,000 ADR. Between 40% and 80% occupancy the cost exactly doubles — the same spread as having or not having a banquet hall. But occupancy is a variable operators can move after opening, whereas capacity is fixed at design by floor area and the banquet-hall decision and cannot be reduced later. The order stays the same: settle the banquet-hall question first in the business plan, and use occupancy sensitivity to stress-test the downside in loan underwriting.

Compared With Sewered Sites — Beneficiary Charges of ¥187 to ¥1,050 per ㎡, With Usage Fees Covered Separately

A hotel inside a sewer district does not pay for a johkasou, but instead pays a beneficiary charge (a one-off levy set by municipal ordinance under Article 75 of the City Planning Act) and sewer usage fees. Beneficiary charges vary widely: Kashiwa charges ¥1,050 per ㎡, Hiroshima ¥187 per ㎡ (outside the urbanization promotion area, a ¥300,000 contribution per final inspection chamber or per city-run johkasou), and Tsuruoka ¥40 to ¥480 per ㎡ depending on the charge zone in the Tsuruoka area. Unlike a johkasou, the charge is levied on land area and applies once service begins, even if the property is not connected.

For a small hotel on a 3,000㎡ site, the beneficiary charge inside a sewer district is ¥560k–¥3.15M, while johkasou installation outside one is ¥13M–¥18M — an upfront gap of more than ¥10M. On ongoing costs, however, the sewered hotel keeps paying usage fees in proportion to water use, while the off-sewer hotel pays ¥630k–¥990k a year in maintenance plus electricity instead. Because usage fees differ by more than 2x between municipalities, the gap narrows in some places over a 20–30-year holding period. For loan underwriting, what matters is where each sits in the accounts: the installation cost is capitalized as depreciable equipment integral to the building, while maintenance hits each period’s P&L as a fixed cost. Equipment booked as depreciable assets also incurs annual depreciable asset tax separate from the building, broken down per room in Hotel Depreciable Asset Tax: ¥21k–¥66k per Room a Year.

Implications for Site Evaluation — Wastewater Infrastructure Is About “What It Costs to Own,” Not “Whether It Exists”

Off-sewer resort sites carry their own wastewater infrastructure capex and holding costs, but pay no beneficiary charges or usage fees. In our estimates the difference is around 1% of revenue — not enough to decide whether a site works. What matters more is building the JIS logic — capacity set by floor area and the banquet-hall decision — into the design from the outset, getting quotes from several contractors in the 51-PE-plus range where no published unit costs exist, and confirming the discharge route (river, roadside ditch, or whether ground infiltration is allowed) at the site-selection stage. When reopening a dormant ryokan, check the existing johkasou’s capacity, treatment method and installation year; if the plan closes a banquet hall, the resulting headroom in the capacity calculation can be put to use in the design. For loan underwriting, the practical approach is to place installation cost in depreciable building equipment and maintenance in fixed costs, and to examine banquet-hall sensitivity before occupancy sensitivity.

How this article fits with our earlier coverage: it deals with the wastewater side, and only outside sewer districts. Water supply via private wells is covered in Hotels Without Mains Water: 20-Year Private Well Costs, 2,120 Sites, heat sources in No City Gas? Heat Costs +¥68,100/Room/Year — 3 Options Priced 2026, sewer usage fees inside sewer districts in Hotel Water & Sewer Costs Vary 2.1x by Municipality, and upfront water connection costs in Hotel Water Connection Fees Vary ¥5.11M by Municipality. Read together, the four infrastructure systems give a full picture of upfront and holding costs for off-grid sites.

Frequently Asked Questions

Q. Outside a sewer district, what johkasou capacity does a 30-room hotel need?

A. Under the JIS A 3302 formula for hotels and ryokan, multiply total floor area by 0.075 (or 0.15 with a banquet or wedding hall). For 1,500㎡ of floor area, that is about 113 PE without a banquet hall and 225 PE with one; the final capacity is set by the practice of the designated administrative agency or designated building confirmation body.

Q. How much does a johkasou cost to install and maintain?

A. The Ministry of the Environment publishes unit costs only up to 50 PE; the standard type for 41–50 PE costs ¥5.737M. Extending ¥115k–¥160k per person, this article gives a reference range of ¥13M–¥18M for 113 PE, with annual maintenance of ¥630k–¥990k (excluding electricity). Above 51 PE there are no published unit costs, so confirm with quotes from several contractors.

Q. Did MLIT’s July 2026 notice change how johkasou capacity is calculated for lodging facilities?

A. No. The July 3, 2026 notice (Kokujushi No. 191) permits johkasou with a design capacity of fewer than 5 persons for detached houses (excluding apartment buildings); the formulas for hotels, ryokan and simple lodging remain those of JIS A 3302.

Q. What must a johkasou administrator do every year?

A. Undergo the periodic inspection under Article 11 of the Johkasou Act once a year, contract maintenance inspections at a frequency set by the treatment method (at least weekly for activated sludge, for example), and desludge at least once a year. After installation, the Article 7 water quality inspection is also required between 3 and 5 months after the start of use.

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*The installation and maintenance costs in this article are reference ranges extended from published unit costs. Actual investment decisions require contractor quotes, prior consultation with the designated administrative agency and a detailed feasibility study. The 60% occupancy rate is an assumed year-round value used for per-room-night conversion, not an actual result.