💧 Real Life Math
Why does your
water bill change every month?
The more water your household uses, the more you pay! For a ½ inch pipe, you pay a minimum charge of Rs. 100 for the first 10 units (10,000 liters) and Rs. 32 per additional unit. Sewerage service charge is 50% of your water charge.
10 units
Minimum Consumption
Rs. 100
Minimum Charge
Rs. 32
Extra per unit
50%
Sewerage Charge
Your Home
00027
Units Consumed
Water ChargeRs. 644
Sewerage (50%)Rs. 322
Total BillRs. 966
Unit (1 unit = 1000 L)
Water consumption is measured in units. 1 unit = 1000 liters = 1 cubic meter. Your water meter records consumption in units. 1000 liters = 1 unit.
Minimum Charge
For ½ inch pipe, minimum consumption is 10,000 L (10 units) with a minimum charge of Rs. 100. Additional units beyond 10 are charged at Rs. 32 per unit.
Sewerage Service
Sewerage charge = 50% of the water consumption tariff. This covers wastewater treatment services provided alongside drinking water supply.
🇳🇵 KUKL — Kathmandu Upatyaka KhanePani Limited
KUKL supplies drinking water to Kathmandu Valley. For a ½ inch pipe connection, the minimum consumption is 10,000 liters (10 units) with a minimum charge of Rs. 100. Additional water consumption beyond 10 units is charged at Rs. 32 per 1000 liters (1 unit). Sewerage charge is 50% of the water charge. Branch: Tripureshwor.
Sewerage = 50% of Water Charge | Pay within 1st–2nd month: 3% discount | 3rd month: as per bill
📋 Tariff rate table applicable from Shrawan 1, 2070
| Size of pipe (in inch) |
Minimum consumption (in litre) |
Minimum unit |
In the meter connected taps | |
|---|---|---|---|---|
| Minimum charge (in Rs.) |
Based on the volume when more water is used (per 1000 litre) Rs. |
|||
| ½" | 10000 | 10 | 100 | 32 |
| ¾" | 27000 | 27 | 1,910 | 71 |
| 1" | 56000 | 56 | 3,960 | 71 |
| 1.5" | 155000 | 155 | 10,950 | 71 |
| 2" | 320000 | 320 | 22,600 | 71 |
| 3" | 881000 | 881 | 62,240 | 71 |
| 4" | 1810000 | 1810 | 1,27,865 | 71 |
Size of pipe
½"
Min. consumption (litre)
10000
Min. unit
10
Minimum charge (Rs.)
100
Rate per 1000 litre (Rs.)
32
Size of pipe
¾"
Min. consumption (litre)
27000
Min. unit
27
Minimum charge (Rs.)
1,910
Rate per 1000 litre (Rs.)
71
Size of pipe
1"
Min. consumption (litre)
56000
Min. unit
56
Minimum charge (Rs.)
3,960
Rate per 1000 litre (Rs.)
71
Size of pipe
1.5"
Min. consumption (litre)
155000
Min. unit
155
Minimum charge (Rs.)
10,950
Rate per 1000 litre (Rs.)
71
Size of pipe
2"
Min. consumption (litre)
320000
Min. unit
320
Minimum charge (Rs.)
22,600
Rate per 1000 litre (Rs.)
71
Size of pipe
3"
Min. consumption (litre)
881000
Min. unit
881
Minimum charge (Rs.)
62,240
Rate per 1000 litre (Rs.)
71
Size of pipe
4"
Min. consumption (litre)
1810000
Min. unit
1810
Minimum charge (Rs.)
1,27,865
Rate per 1000 litre (Rs.)
71
Note: 50% tariff is fixed for the sewage service being taken by the company at the tariff.
The above bill is calculated at the following tariff rate. According to the rules, a minimum of 10000 litre or 10 units of water (1 unit = 1000 litre) is consumed in a ½ inch pipe.
💰 Payment Exemption & Penalty Schedule
| Payment Period (by the date bill is distributed) | Discount / Fine |
|---|---|
| Within the first and second month | 3% Discount |
| Within the third month | As per bill |
| Within the fourth month | 10% Fine |
| Within the fifth month | 20% Fine |
| After the fifth month | 50% Fine |
🔄 How Is Your Water Bill Calculated?
1
Read the Meter
Units consumed = Present reading − Previous reading. (1 unit = 1000 liters)
2
Calculate Water Charge
If consumption ≤ minimum units: Water Charge = Minimum Charge. If consumption > minimum units: Water Charge = Min. Charge + (units − min. units) × extra rate.
3
Add Sewerage Charge
Sewerage Charge = 50% of Water Charge.
4
Apply Discount or Fine
1st–2nd month: 3% discount. 3rd month: as per bill (no change). 4th month: 10% fine. 5th month: 20% fine. After 5th month: 50% fine.
5
Final Payable Amount
Final Amount = (Water Charge + Sewerage Charge) − Discount OR + Fine
📐 Formula 1 — Units Consumed
Units Consumed = Present Reading − Previous Reading
Water meter reading in units (1 unit = 1000 liters). Read from the meter at end of month minus previous month's reading.
📐 Formula 2 — Water Charge (½ inch pipe)
If units ≤ 10: Water Charge = Rs. 100 (minimum charge)
If units > 10: Water Charge = 100 + (Units consumed − 10) × 32
Minimum charge = Rs. 100 for first 10 units. Extra rate for ½" pipe = Rs. 32 per additional unit.
📐 Formula 3 — Sewerage Charge
Sewerage Charge = 50% of Water Charge = (Water Charge × 50) ÷ 100
Sewerage service charge is always 50% of the water consumption tariff for all pipe sizes.
📐 Formula 4 — Total Bill Amount
Total Bill = Water Charge + Sewerage Charge
This is the base total before any discount or penalty is applied.
📐 Formula 5 — Discount / Fine & Final Payable
1st–2nd month: Discount = 3% of Total Bill → Final = Total Bill − Discount
3rd month: No change → Final = Total Bill (as per bill)
4th month: Fine = 10% of Total Bill → Final = Total Bill + Fine
5th month: Fine = 20% of Total Bill → Final = Total Bill + Fine
After 5th month: Fine = 50% of Total Bill → Final = Total Bill + Fine
📐 Formula 6 — For Other Pipe Sizes (¾", 1", 1.5", 2", 3", 4")
If units ≤ min. units: Water Charge = Minimum Charge
If units > min. units: Water Charge = Min. Charge + (Units − Min. Units) × 71
Extra rate for ¾" and above = Rs. 71 per additional unit.
Example 1 of 3
A ½ inch water pipe is connected to the house of Siddhibabu. The present reading of the meter in the month of Chaitra is 3754 units and the previous reading is 3727 units. If the bill is paid in the second month of Chaitra, find the total tariff to be paid including 50% sewerage charge.
Present Reading = 3754
Previous Reading = 3727
Paid within 2nd month (3% discount)
½ inch pipe
✏️ SOLUTION
1
Units consumed = 3754 − 3727 = 27 units
2
Minimum charge = Rs. 100 at the rate of Rs. 32 per unit
Water Charge = 100 + (27 − 10) × 32 = 100 + 17 × 32 = 100 + 544 = Rs. 644
Water Charge = 100 + (27 − 10) × 32 = 100 + 17 × 32 = 100 + 544 = Rs. 644
3
Sewerage Charge = 50% of Rs. 644 = Rs. 644 × 50/100 = Rs. 322
4
Total Amount = Rs. 644 + Rs. 322 = Rs. 966
5
As per the rule, Siddhibabu is paying in the second month of Chaitra, so he gets a discount of 3%.
Discount = 3% of Rs. 966 = Rs. 966 × 3/100 = Rs. 28.98
Discount = 3% of Rs. 966 = Rs. 966 × 3/100 = Rs. 28.98
6
∴ The amount to be paid by Siddhibabu in the second month = Rs. 966 − Rs. 28.98 = Rs. 937.02
✅ Total Amount to Pay = Rs. 966 − Rs. 28.98 = Rs. 937.02
Example 2 of 3
423 units of water was consumed in a month at a hotel from Central Colony from a 1.5 inch sized water supply pipe. If the bill is paid within the fourth month from the bill distribution date, how much total fine amount is to be paid?
Units = 423 units
Pipe = 1.5 inch
Min. units = 155
Min. charge = Rs. 10,950
Extra rate = Rs. 71/unit
Paid 4th month (10% fine)
✏️ SOLUTION
1
Tariff for consumption of 423 units at the rate of Rs. 71 per unit beyond minimum:
Extra units = 423 − 155 = 268 units
Extra units = 423 − 155 = 268 units
2
Water Charge = 10,950 + (423 − 155) × 71 = 10,950 + 268 × 71 = 10,950 + 19,028 = Rs. 29,978
3
50% Sewerage Charge = 50% of Rs. 29,978 = Rs. 14,989
4
Total Bill = Rs. 29,978 + Rs. 14,989 = Rs. 44,967
5
If paid within the fourth month, an additional 10% fine is levied.
Fine = 10% of Rs. 44,967 = Rs. 4,496.70
Fine = 10% of Rs. 44,967 = Rs. 4,496.70
6
∴ Total amount payable = Rs. 44,967 + Rs. 4,496.70 = Rs. 49,463.70
✅ Final Amount to Pay (with 10% fine) = Rs. 49,463.70
Example 3 of 3
There is a ½ inch drinking water supply pipe in Kopila's house. The current and previous reading in the month of Shrawan are 4225 and 4197 respectively. Answer the following questions on the basis of the tariff table given on the previous page:
(a) How much does Kopila have to pay for this month's sewerage service?
(b) If the bill is paid within the first and second months of distribution, how much tariff does she have to pay?
(c) If the bill is paid within the fifth month, how much fine is there to pay?
(a) How much does Kopila have to pay for this month's sewerage service?
(b) If the bill is paid within the first and second months of distribution, how much tariff does she have to pay?
(c) If the bill is paid within the fifth month, how much fine is there to pay?
Present Reading = 4225
Previous Reading = 4197
½ inch pipe
✏️ SOLUTION
1
Units consumed = 4225 − 4197 = 28 units
2
Water Charge = 100 + (28 − 10) × 32 = 100 + 18 × 32 = 100 + 576 = Rs. 676
3
(a) Sewerage Charge = 50% of Rs. 676 = Rs. 676 × 50/100 = Rs. 338
4
Total Bill = Rs. 676 + Rs. 338 = Rs. 1,014
5
(b) Paid within 1st–2nd month (3% discount):
Discount = 3% of Rs. 1,014 = Rs. 1,014 × 3/100 = Rs. 30.42
Amount payable = Rs. 1,014 − Rs. 30.42 = Rs. 983.58
Discount = 3% of Rs. 1,014 = Rs. 1,014 × 3/100 = Rs. 30.42
Amount payable = Rs. 1,014 − Rs. 30.42 = Rs. 983.58
6
(c) Paid within 5th month (20% fine):
Fine = 20% of Rs. 1,014 = Rs. 1,014 × 20/100 = Rs. 202.80
Amount payable = Rs. 1,014 + Rs. 202.80 = Rs. 1,216.80
Fine = 20% of Rs. 1,014 = Rs. 1,014 × 20/100 = Rs. 202.80
Amount payable = Rs. 1,014 + Rs. 202.80 = Rs. 1,216.80
✅ (a) Sewerage = Rs. 338 | (b) With 3% discount = Rs. 983.58 | (c) With 20% fine = Rs. 1,216.80