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By Jason Lim, REN 84424 · IQI Realty · Checked on 15 November 2026
This guide is for owners and buyers of landed homes in Johor Bahru, whether Malaysian or from Singapore, Indonesia, India, China or elsewhere. The short answer: a rainwater harvesting system (sistem pengumpulan dan penggunaan semula air hujan, SPAH) collects roof rain in a covered tank for gardens, car washing and other non-drinking uses. Under the 2012 Uniform Building By-Laws amendment, new bungalows, semi-detached houses and detached buildings with a roof of 100 m² or more must have one in states that adopted it; for terraces and existing homes it is optional. Keep the tank sealed, or it becomes a mosquito breeding spot.
Quick answer
- When it is required: new semi-Ds, bungalows and detached buildings with a roof of 100 m² or more, in states that gazetted the UBBL amendment (KPKT reply to Parliament, 2019).
- Johor: MBJB’s housing guideline says SPAH must follow the 2012 amendment and encourages it for roofs of 100 m² or more, terraces included.
- Uses: non-drinking only: garden, car and floor washing, and toilet flushing through separate pipes.
- How much: about 1 litre per m² of roof for every 1 mm of rain, before losses. JB gets roughly 2,100 mm a year.
- Savings: NAHRIM research cited by the water ministry found up to 30% of treated water use can be saved (December 2025).
- Mosquitoes: Aedes needs only about 2 cm of clean water (MOH, July 2026); breeding on your premises can mean a fine of up to RM10,000 under Act 154.
What a home rainwater system is
Rain runs off the roof into gutters and downpipes, through a leaf screen, into a covered tank. A tap or small pump sends it to a hose, an outdoor tap or the toilet cisterns, and an overflow pipe takes the excess to the drain. It is not the roof-space tank that stores Ranhill SAJ’s treated water for your bathrooms (see water tank cleaning for landed homes). Rainwater is untreated and must stay completely separate from the treated supply.
The rules: when SPAH is required
The housing ministry issued rainwater guidelines in 1999. Making it compulsory came through the Uniform Building By-Laws 1984 (UBBL), which each state has to gazette itself.
| Date | What happened | What it means for you |
|---|---|---|
| 13 June 2011 | The housing minister announced that new bungalows, semi-detached homes and government buildings must have rainwater systems, after the National Council for Local Government approved it on 23 May 2011 | Plans without a system would not be approved; existing buildings were only encouraged |
| 2012 | UBBL amendments introduced SPAH (by-laws 2, 10 and 115) | The legal basis councils use when checking plans |
| July 2019 sitting | KPKT told Parliament that 10 states had gazetted the amendment, compulsory only for semi-Ds, bungalows and detached buildings with a roof of 100 m² or more; 2,677 projects and 16,668 buildings had installed SPAH in 2015–2018 | Terraces, condos and existing homes are outside the compulsory rule |
| 15 December 2025 | The water transformation minister said 11 Peninsular states had adopted the amendment and that support for household installation would be discussed with the Ministry of Finance | A proposal only; nothing announced for households as of November 2026 |
What it means in Johor
Majlis Bandaraya Johor Bahru’s housing planning guideline (Garis Panduan Perancangan: Perumahan, file dated February 2023) says SPAH must follow the Uniform Building (Amendment) By-Laws 2012 and encourages it for roofs of 100 m² or more across most house types, from bungalows to terraces and condominiums.
If you buy a new semi-D or bungalow, ask whether a system was in the approved plans and where it is. If you build your own house, your architect or engineer handles SPAH in the plan submission; see buying land to build a house in Johor, when you need an architect or engineer and JB’s local councils explained.
How much water can your roof collect?
1 mm of rain on 1 m² of roof is 1 litre. Some is lost to splashing, evaporation and the first dirty flush, so the examples assume you keep 80%. Use the roof’s plan area seen from above. The nearest published long-term rainfall record is Singapore’s Changi station: about 2,100 mm a year (1991–2020 means), wettest in December (about 332 mm) and driest in February (about 105 mm), per the Meteorological Service Singapore. See JB’s weather and monsoons.
| Illustration (100 m² roof) | Rain | Collected at 80% |
|---|---|---|
| One heavy afternoon storm | 25 mm | About 2,000 litres (2 m³) |
| A typical February | 105 mm | About 8,400 litres |
| A typical December | 332 mm | About 26,600 litres |
| A whole year | 2,113 mm | About 169,000 litres |
Tank size. Because JB rain is frequent, a tank that refills every few days can be modest. Size it for the use: weekly garden watering needs far less than toilet flushing for a family of five. 1,000 litres weighs about a tonne, so the tank needs a firm, level base at ground level. NAHRIM, the national water research institute, publishes a design guide (Technical Guide No. 2, 2015) and tank-sizing software that the water ministry mentioned in December 2025; your designer or plumber can use them.
What you can use it for, and what not
| Use | Suitable? | Notes |
|---|---|---|
| Watering plants | Yes | The most common use; see my garden and landscaping guide |
| Washing the car, porch and drains | Yes | A tap near the porch is handy |
| Toilet flushing | Yes, with separate pipework | Needs its own pipes and usually a pump; easiest during building or a major renovation |
| Drinking, cooking, brushing teeth | No | Roof rain picks up dust, leaves and bird droppings; official statements describe SPAH water as non-potable |
Never connect a rainwater pipe to the treated-water pipes from the meter, because a cross-connection can push untreated water into your drinking supply. Use a licensed plumber, mark the pipes and label rainwater taps “not for drinking”. See plumbing in older homes and tap water and filters in JB.
Will it cut your water bill?
A little, more for heavy users. Ranhill SAJ charges domestic users RM1.05 per m³ for the first 20 m³ a month, RM2.35 for 21 to 35 m³ and RM3.50 above 35 m³, with a RM10.50 minimum (checked November 2026). Replacing 5 m³ a month saves about RM5.25, RM11.75 or RM17.50 depending on your block (my illustration). The bigger gains are a backup during water cuts and less storm runoff. See electricity and water bills in JB and water supply disruptions in Johor.
Parts of a typical home system
- Gutters and downpipes, kept clear; see blocked drains in the monsoon and roof leaks.
- Leaf screen and first-flush diverter, which keep debris and the dirtiest first rain out of the tank.
- Opaque tank with a sealed, lockable lid; light encourages algae, and an outlet set above the floor leaves sediment behind.
- Screened overflow and vents, with the overflow running into a drain, not against your wall or a neighbour’s.
- Outlet tap or pump: gravity works for a hose; toilets or upper floors need a pump.
Urban rainwater tends to be acidic, so materials must cope with it (Bernama, 11 March 2025). I don’t recommend any brand or installer, and I found no reliable, dated cost range for Johor, so compare at least two written quotes.
Looking at semi-Ds or bungalows in JB?
Tell me the area and your budget. When we view, I ask whether the house has a rainwater system, where the tank is and how the garden and drains cope in heavy rain.
WhatsApp JasonKeeping the tank clean and mosquito-free
The Ministry of Health says Aedes needs only about 2 cm of clean standing water to breed (RTM, July 2026), and a tank with a loose lid or unscreened overflow is exactly that. Under the Destruction of Disease-Bearing Insects Act 1975 (Act 154), a first offence can mean a fine of up to RM10,000, up to two years’ jail, or both, and owners and occupiers can both be liable. See my mosquito and dengue guide.
| How often | What to do |
|---|---|
| Weekly | Lid closed, mesh intact, no larvae in any open water around the system |
| After storms | Clear gutters, screens and the first-flush diverter; check the overflow drains away |
| Before the northeast monsoon (about October) | Clean gutters and downpipes; check the tank base and fittings for cracks |
| About once a year | Drain and clean out sludge, or sooner if the water smells or turns green |
Children and pets. An environmental association warned about children getting into storage tanks (Bernama, 11 March 2025), so fit a lid they cannot open. If you will be away for months, see my vacant home checklist.
Before you add one to an existing home
- Decide the use: garden only, or toilets too. That sets tank size and pipework.
- Pick a firm, level spot near a downpipe, clear of the porch, drains and party wall.
- Check approvals. A garden tank is usually simple, but a concrete plinth, roof-mounted tank or drain changes may need council approval; see my renovation permit guide. Gated estates may have design rules; see gated and guarded homes.
- Get a written quote covering the tank, screens, diverter, pump and base.
Condos and rented homes
Condos. A building-wide system is common property, run by the joint management body (JMB) or management corporation (MC) under the Strata Management Act 2013 and paid for from maintenance fees. Tanks on balconies or common areas usually breach the by-laws. Ask management whether the system works; see checking condo management before buying. Rented houses. The tenancy agreement should say who clears screens and gutters and who repairs the pump; see who pays for repairs.
What I check when a house has a system
| Check | What to ask or look for |
|---|---|
| Approved plan | For a newer semi-D or bungalow, whether the system was in the approved building plan |
| Tank, lid and mesh | No cracks or leaks, a lid that closes, mesh on the overflow and vents |
| Water and pump | No green water, smell or larvae; the pump works and pipes are separate and labelled |
| Gutters, drains and records | Gutters clear, no ponding near walls; when the tank was last cleaned |
Raise any problem before you make an offer. See my subsale house inspection guide, questions to ask at a viewing and landed home running costs.
Where to buy if this matters to you
- Iskandar Puteri: newer townships with semi-Ds and bungalows.
- Bukit Indah and Gelang Patah: gated landed estates with larger gardens.
- Mount Austin: family area with landed phases of different ages.
- Tebrau, Setia Indah and Molek: established homes where a system would be a retrofit.
- Kulai and Senai: larger plots with room for a tank.
Compare them on my JB property map and check flood risk in JB. Foreigners can generally buy Johor homes only from RM1 million, with only limited exceptions (for example, some serviced apartments sold by developers with state approval); no area is exempt as a whole. See Johor’s foreigner minimum price.
More Johor living guides: Water tank cleaning for landed homes · Gardens and landscaping in JB · Mosquitoes and dengue at home · Water supply disruptions in Johor
Frequently asked questions
Is rainwater harvesting compulsory for houses in Johor?
For new semi-detached houses, bungalows and detached buildings with a roof of 100 m² or more, the 2012 UBBL amendment requires it in states that gazetted it, and MBJB’s guideline says SPAH must follow that amendment. Terraces, condos and existing homes are not required to add one, though MBJB encourages it.
Can I drink harvested rainwater?
No. Roof rain picks up dust, leaves and bird droppings, and official statements describe SPAH water as non-potable. Use it for gardens, washing and toilet flushing through separate pipes.
How much rainwater can my roof collect?
About 1 litre per m² of roof plan area for every 1 mm of rain, before losses. As an illustration, a 100 m² roof keeping 80% collects about 2,000 litres from a 25 mm storm. Your tank size limits how much you store.
Does a rainwater tank breed mosquitoes?
It can if the lid is loose or the overflow and vents are not screened, because Aedes needs only about 2 cm of clean water. Keep it sealed, check weekly and clear gutters. Breeding on your premises can lead to a fine under Act 154.
Do I need council approval to install a rainwater tank?
A small tank standing in the garden is usually simple, but a concrete base, a roof-mounted tank or drain changes may need approval. Ask your council (MBJB, MBIP, MPKu or MBPG) and your estate management first.
Will rainwater harvesting cut my water bill much?
Modestly. Replacing 5 m³ a month saves about RM5.25 to RM17.50 depending on your Ranhill SAJ tariff block. The backup during water cuts is often worth more.
Can condo residents harvest rainwater?
Usually not individually, as balconies and common areas are covered by the by-laws. A building-wide system is common property run by the JMB or MC; ask management whether the building has one.
Looking for a landed home with room for a garden?
Tell me the area, the type of house and your budget. When we view, I check whether the house has a rainwater system or space for one, look at the gutters, drains and garden, and ask the owner about water cuts and upkeep. You can also book an appointment for viewings, or a Zoom consultation if you are still abroad.
Sources: KPKT, written reply to Dewan Rakyat question 337 on rainwater harvesting since the 2012 UBBL amendments, July 2019 parliamentary sitting; The Star, “New bungalows, semi-detached homes, govt buildings must have rain water systems”, 13 June 2011 (republished by Eco-Business); Bernama via theSun, “Rainwater harvesting system aids sustainable water management and flood control”, 15 December 2025; Bernama, experts on rainwater harvesting after the Prime Minister’s directive, 11 March 2025; Majlis Bandaraya Johor Bahru, Garis Panduan Perancangan: Perumahan (file dated February 2023), accessed November 2026; Universiti Sains Malaysia, list of rainwater harvesting guidelines in Malaysia (incl. NAHRIM Technical Guide No. 2, 2015), accessed November 2026; Meteorological Service Singapore, Climate of Singapore (Changi climate station, 1991–2020 long-term means), accessed November 2026; Berita RTM, “Luang 10 minit seminggu periksa kawasan rumah cegah denggi” (MOH Disease Control Division), 20 July 2026; Attorney General’s Chambers, Laws of Malaysia: Destruction of Disease-Bearing Insects Act 1975 (Act 154) and Strata Management Act 2013 (Act 757), checked November 2026; Ranhill SAJ, water tariff (domestic blocks and RM10.50 minimum), checked November 2026
Jason Lim, REN 84424, IQI Realty Sdn. Bhd. E (1) 1584/6. General information checked on 15 November 2026, not legal, plumbing or engineering advice. Rules and guidance change; confirm with your local council, a licensed plumber or engineer, and the system designer before you install or rely on a system.