Many apartment communities water their gardens with treated water from their own sewage treatment plant (STP). It saves a large amount of fresh water, which matters in a city where summer water supply is a real worry. It also changes how the garden behaves over the years. As a first-time buyer, you will be paying towards this system through maintenance charges, so it helps to know how it works and what good looks like.
The loop, simply
Used water from kitchens, bathrooms and washing machines flows to the STP. There it is treated in stages: solids settle, bacteria break down the waste, and the water is filtered and disinfected. The treated water is stored in a tank. From there, it is pumped to the garden through drip lines or sprinklers, and in many projects to toilet flushing too. Water that would have left the site is used again.
A worked example: how much water is in play (illustrative)
Take a made-up community of 100 flats with four people each.
- India's water supply planning commonly uses 135 litres per person per day for urban homes with full flushing. That is the figure in the CPHEEO manual of the Ministry of Housing and Urban Affairs.
- 400 people × 135 litres = 54,000 litres a day of water used.
- Planners usually assume about 80% of supplied water returns as wastewater. 54,000 × 0.8 = 43,200 litres a day reaching the STP.
- If the garden needed, say, 10,000 litres a day, treated water could cover it with plenty to spare for flushing.
Now put a price on it. If a 6,000-litre tanker cost ₹1,000, then 10,000 litres a day would be about ₹1,667 a day, or roughly ₹6 lakh a year, spread across the community. The tanker price is made up for the sum. The point is that a working STP is not just green; it keeps maintenance bills down.
What it does to soil over time
Treated water can carry more dissolved salts than fresh water. Over the years, salts can build up in the soil and stress plants. Good drainage, occasional flushing with rain or fresh water, and hardy plants help keep the garden healthy. Soil that turns white or crusty on top is an early sign of salt build-up.
Plants that cope, and plants that struggle
Local, hardy trees, shrubs and grasses tend to handle recycled water well. Very delicate ornamental plants may struggle. A landscape planned for recycled water from the start usually looks better in year five than one that was not.
Why it runs when it does
Irrigation often runs early in the morning or late in the evening. Less water evaporates, paths are dry by the time people walk, and fewer people are on the lawns. That suits families with small children too.
Drip, sprinklers or underground lines
- Drip: water goes straight to the roots. Efficient, and less contact with people.
- Underground lines: water stays below the surface. Good for lawns.
- Sprinklers: spread water widely. Simple, but more spray in the air.
Step by step: checking the system on a visit
- Ask where the STP is and whether you can see it. It should be fenced and away from play areas and windows.
- Ask for its capacity in kilolitres per day, and how that compares with the number of homes.
- Ask for test reports. A well-run plant tests its treated water regularly. Ask to see recent results.
- Check the pipes. Treated-water lines and taps should be clearly marked so nobody drinks from them.
- Walk the garden in a ready community by the same builder. Look at the plants and smell the air.
- Ask who runs it after handover and what the annual cost is.
Healthy system or struggling one?
On a visit to a ready community, look for green, even plants, dry paths and no smell. Warning signs are yellow or patchy plants, soggy spots that never dry, blocked sprinklers and a sewage smell near lawns.
Common mistakes first-time buyers make
- Not asking about the STP at all. It is one of the biggest running costs in a community.
- Assuming it runs itself. It needs a trained operator, power and regular servicing.
- Ignoring the location. A flat right above or beside the STP may get noise or smell.
- Forgetting power backup. If the STP stops in a power cut, untreated water can back up.
Questions to ask
- Is the garden watered with treated STP water?
- What irrigation method is used, and at what times?
- Can I see recent treated-water test reports?
- Who maintains the garden and the system after handover, and at what cost?
Is treated water safe around children?
Treated water from a well-run STP is meant for uses like gardens and flushing, not for drinking. Pollution control boards set the discharge and reuse limits a plant must meet, and the operator should test against them. The sensible precautions are simple: irrigation outside play hours, no treated-water taps within children's reach, and clear signs on any tap that carries it. Ask the builder which of these they plan.
What it adds to maintenance
An STP needs electricity for its pumps and blowers, a trained operator, regular cleaning and sludge removal, and spare parts. These costs come out of the monthly maintenance you pay. Ask for an estimate of the yearly running cost and how it is split across homes. A plant that is run properly costs money; a plant that is ignored costs more later.
Rainwater and recycled water together
Many communities combine both. Rainwater is collected from roofs and paved areas and sent to recharge pits or tanks, while treated water serves the garden. Rain also helps flush salts out of the soil, which is one reason gardens often look their best after the monsoon. Ask whether the project has rainwater harvesting and where the recharge pits are.
After you move in
Once you live there, join the residents' association meetings when the STP is discussed. Ask for the operator's log and the yearly test results. A few residents who understand the system make it much more likely to keep running well.
Your recycled-water checklist
- STP location seen and away from homes and play areas
- Capacity noted
- Recent test reports seen
- Treated-water pipes and taps marked
- Irrigation method and timing known
- Handover and running-cost plan in writing
Low-density communities leave more open land for gardens. See how ours is planned at The Shalott Marque.