Chlorine
Still water.
Impossibly clean.
White-gloved pool maintenance for Minato-ku condominiums, boutique hotels, and international schools — bilingual service, every season.
Ready to hand it over to the experts?
How often do outdoor pools need balancing during tsuyu season?
Tokyo's rainy season (梅雨, typically June 10 – July 20) delivers 200mm+ of rainfall in six weeks. Every millimetre of rain that hits your pool is essentially distilled water — it contains zero minerals, zero buffering capacity.
This dilutes your pool's Total Alkalinity (TA) faster than any other season. Low TA means pH becomes unstable and volatile — bouncing between 6.8 and 8.2 within the same week. At 6.8, chlorine loses 80% of its sanitising effectiveness. At 8.2, it forms chloramines that irritate guests' eyes and corrode stainless fittings.
Our tsuyu protocol: weekly pH and TA testing, sodium bicarbonate top-ups after every significant rainfall event (>20mm), and a pre-season alkalinity buffer treatment applied in late May.
pH Scale — Pool Chemistry
Ideal pool range: 7.2–7.6. During tsuyu (June–July), Tokyo's heavy rainfall dilutes bicarbonate alkalinity, pushing pH below 7.0 within days. Weekly balancing is the minimum.
Recommended Balancing Frequency
Is ozone safer than chlorine for a children's pool?
The short answer: an ozone-chlorine hybrid system is the gold standard for children's facilities — and for luxury hotel pools where guest comfort matters as much as sanitation.
Ozone (O₃) is one of the most powerful oxidisers known. It destroys chlorine-resistant parasites like Cryptosporidium in under 30 seconds — something chlorine alone cannot do. It also eliminates the chloramines (combined chlorine) responsible for that "pool smell" and the red eyes that guests complain about.
Because ozone does the heavy lifting, residual chlorine can be kept at 0.3–0.5 ppm (vs. the standard 1.5–3 ppm) — well below the level that irritates sensitive skin. Tokyo's Hokenjo inspectors accept ozone hybrid systems provided a measurable chlorine residual is maintained. We handle all documentation.
For international school pools:
We recommend UV-C in addition to ozone for facilities used by children under 5. UV-C adds a third kill step with zero chemical residual. Ask about our School Safe package.
Ozone + Chlorine Hybrid System — Cross-Section
Ozone vs Chlorine-Only
Ozone Hybrid
Chlorine Only
Now that you know what tsuyu does to alkalinity…
Ready to hand it over to the experts?
What does a Hokenjo inspection actually check?
The Hokenjo (保健所) — your ward's public health centre — inspects swimming pools under the Swimming Pool Hygiene Standards (プール衛生管理の手引き). Inspectors arrive unannounced, typically between June and September.
The core focus is water quality: free chlorine residual, pH, turbidity, and coliform bacteria. But inspectors also check your filtration turnover rate, your chemical storage log, and whether depth markings are clearly visible.
Failure triggers a mandatory closure notice (使用禁止命令) served the same day. For a boutique hotel or luxury condominium, that means calling every guest to apologise. We've seen it happen to properties that thought their pool "looked fine."
Our service includes weekly water quality logs formatted to Hokenjo standards, pre-inspection audits, and bilingual communication with your ward office. Every Chlorine client who has faced an inspection has passed on the first visit.
Hokenjo Inspection Checklist
公衆浴場法 CompliantWater Quality
Circulation & Filtration
Facility & Safety
We file the paperwork. You attend the inspection.
Chlorine prepares bilingual (日英) inspection reports and pre-submits water quality data to your ward office. Our clients have a 100% first-visit pass rate.
What does a full year of pool maintenance actually look like in Tokyo?
Most pool service companies sell you a fixed monthly visit. Tokyo's climate makes that approach inadequate. Your pool in January is a different organism from your pool in July — the chemistry, the biology, and the inspection obligations are all different.
We structure our maintenance plans around Tokyo's actual seasonal calendar: winter hibernation, spring start-up, tsuyu intensive care, summer peak management, and autumn wind-down. Each phase has its own chemical protocol, equipment service schedule, and documentation requirements.
The calendar diagram shows a typical annual programme for a rooftop infinity pool in Minato-ku. Indoor pools (hotel basement, ryokan) follow a slightly different cadence — ask us about your specific facility type.
"We switched to Chlorine after failing a Hokenjo inspection with our previous provider. Since then — three inspections, three passes, all first visit. The seasonal calendar approach is what makes the difference."
Robert Müller
General Manager, Minato-ku Boutique Hotel
Annual Maintenance Calendar — Tokyo
You've just read what a year of professional pool care actually involves.
Ready to hand it over to the experts?
Structured around Tokyo's seasons,
not a generic visit schedule.
All plans include bilingual service, chemistry documentation, and a technician who understands the difference between a tsuyu alkalinity crash and a filter backwash issue.
Essentials
エッセンシャル
For indoor lap pools and condominium amenity pools with low seasonal exposure.
- 2 visits per month
- pH, chlorine & TA testing
- Chemical top-ups included
- Monthly PDF report
- Email support (bilingual)
Seasonal+
シーズナル+
For rooftop and outdoor pools. Tsuyu-intensive protocol, pre-Hokenjo audit included.
- 4 visits/month (6 in tsuyu)
- Full chemistry panel + turbidity
- Hokenjo-format water reports
- Pre-inspection bilingual audit
- Priority WhatsApp & LINE support
- Alkalinity buffer treatment (May)
White Glove
ホワイトグローブ
For hotel pools, ryokan onsen, and international school facilities with compliance obligations.
- Unlimited visits
- Dedicated bilingual technician
- Hokenjo filing & ward liaison
- Ozone/UV-C system management
- Same-day emergency response
- Annual facility audit report
All prices exclude consumption tax (10%). Minimum 3-month contract. Service area: Tokyo 23 wards.