How to split the water tanker bill by meter

In short: read every meter on the same day each month, work out each flat's litres, decide whether the common meter is shared equally or left out, and give each flat the same share of the tanker cost as its share of the water.

Before you start

• One water meter per flat, on the line from the overhead tank, and a common meter for the garden, common taps or staff quarters if you have one.
• Know each meter's unit. Most show litres; some show cubic metres (kL), where 1 m³ = 1,000 litres.
• Agree in the committee how the common meter's water is handled (step 3), and use the same rule every month.

Step 1: take the readings

Read every meter on the same day each month, usually the last day. Write down the full number on the dial, not the difference, and take a photo of each meter so anyone can check later.

Step 2: work out each flat's usage

Usage = this month's reading − last month's reading, converted to litres. A reading lower than last month's means something happened to the meter; see problems and fixes.

Step 3: decide about the common meter

• Share it equally: add an equal part of the common usage to every flat. This is the usual choice.
• Leave it out: split the tanker cost only by the flats' own meters. Every flat then pays a little more per litre.

Step 4: each flat's share

Flat's water share = tanker cost × flat's usage ÷ total usage. Round to paise and let the last flat take the few paise left over, so the shares add up to the tanker bill exactly.

Worked example: ₹9,000 of tankers in September

Eight flats, and a common meter that used 4,000 litres. Total usage is 33,000 litres. Shared equally, the common water adds 500 litres to each flat. The cost works out at about ₹0.27 a litre.

Flat	Own usage	With common share	Water share
101	3,200 L	3,700 L	₹1,009.09
102	5,100 L	5,600 L	₹1,527.27
201	2,400 L	2,900 L	₹790.91
202	4,000 L	4,500 L	₹1,227.27
301	1,800 L	2,300 L	₹627.27
302	6,500 L	7,000 L	₹1,909.09
401	2,900 L	3,400 L	₹927.27
402	3,100 L	3,600 L	₹981.83 (last flat, takes the remainder)
Total	29,000 L + 4,000 L common	33,000 L	₹9,000.00

Flat 302 used the most water and pays ₹1,909.09; flat 301 used the least and pays ₹627.27. An equal split would have charged every flat ₹1,125. If the common meter were left out instead, the shares would run from ₹558.62 (301) to ₹2,017.24 (302).

The rest of the bill (watchman, electricity, lift and so on) is still shared the usual way: see how to calculate apartment maintenance. In this building that leaves ₹19,685 to share after ₹210 of interest, ₹2,460.63 per flat, so flat 101's bill with a ₹500 corpus is ₹3,969.72.

Problems and fixes

• Missing reading: estimate from earlier months, and mark it as an estimate on the bill.
• Meter replaced or reset: count the old meter up to its last reading, then the new one from its first reading.
• Dial rolled over (went past its maximum back to 0): count up to the maximum, then add the new reading.
• Reading lower than last month: check the photo. It's a typo, a reset or a new meter.
• Stuck meter: estimate this month and get it repaired.

Do it in Socify

Record readings with a photo from Home › Reading and see at a glance which meters still need one. The bill splits the tanker cost by meter, shares or leaves out common meters, handles resets, replaced meters and rollovers, and marks estimates. Residents see their litres and their water share on the bill.