WATER SUPPLY SERVICE LEVEL AND 24X7 EXPECTATIONS

A.    Service level and 24x7 concepts

Water supply service level has been defined for urban and rural areas in the CPHEEO Manual.

Sr. No.	Service level area	Range	LPCD	Type of area	Minimum Pressure in m
1	Urban	Up to population 1000000	70	Single floor Housing	7
2	Urban	Up to population 1000000	70	Double floor Housing	12
3	Urban	Up to population 1000000	70	Triple floor Housing	17
4	Urban	More than 1000000 population	135	Single floor Housing	7
5	Urban	More than 1000000 population	135	Double floor Housing	12
6	Urban	More than 1000000 population	135	Triple floor Housing	17
7	Urban	Up to population 1000000 with sewerage scheme contemplated	135	Single floor Housing	7
8	Urban	Up to population 1000000 with sewerage scheme contemplated	135	Double floor Housing	12
9	Urban	Up to population 1000000 with sewerage scheme contemplated	135	Triple floor Housing	17
10	Urban	More than 1000000 population with sewerage scheme contemplated	150	Single floor Housing	7
11	Urban	More than 1000000 population with sewerage scheme contemplated	150	Double floor Housing	12
12	Urban	More than 1000000 population with sewerage scheme contemplated	150	Triple floor Housing	17
13	Rural	Stand post	40	……………..	3
14	Rural	House connections,	40	Single floor	7
15	Rural	House connection,	55	Single floor	7
16	Rural	House connection	70	Single floor	7

In the above statement the population figures are the projected design populations. In such cases most of the urban areas are covered under the remark of “Sewerage scheme is contemplated.”

B.     Considering the cases for 24x7 level supplies

1.      Case I

In case of urban areas with 70 LPCD water supply for 24x7 supplies, days water supply for the household with 5 persons per house works out to 350 Lit/day.

If the supply is 24 hours then average hourly supply is 350/24 = 14.6 lit/hr.

If the supply is 24 hours then average supply per minute = 14.6/60 = 0.24 lit/min.

Considering peak factor of 3 for this area this supply in peak hours will be = 0.24*3 = 0.72 lit/min.

Even during peak hours the one bucket of 15 Lit capacity will be filled with water in 15/0.72 = 20 min.

2.      Case II

In case of urban areas with 135 LPCD water supply for 24x7 supplies, days water supply for the household with 5 persons per house works out to 675 Lit/day.

If the supply is 24 hours then average hourly supply is 675/24 = 28.12 lit/hr.

If the supply is 24 hours then average supply per minute = 28.12/60 = 0.46 lit/min.

Considering peak factor of 3 for this area this supply in peak hours will be = 0.46*3 = 1.38 lit/min.

Even during peak hours the one bucket of 15 Lit capacity will be filled with water in 15/1.38 = 10.86 min.

3.      Case III

In case of urban areas with 150 LPCD water supply for 24x7 supplies, days water supply for the household with 5 persons per house works out to 750 Lit/day.

If the supply is 24 hours then average hourly supply is 750/24 = 31.25 lit/hr.

If the supply is 24 hours then average supply per minute = 28.12/60 = 0.52 lit/min.

Considering peak factor of 3 for this area this supply in peak hours will be = 0.46*3 = 1.56 lit/min.

Even during peak hours the one bucket of 15 Lit capacity will be filled with water in 15/1.56 = 9.61 min.

4.      Case IV

In case of Rural areas with 40 LPCD water supply for 24x7 supplies, days water supply for the household with 7 persons per house works out to 280 Lit/day.

If the supply is 24 hours then average hourly supply is 280/24 = 11.70 lit/hr.

If the supply is 24 hours then average supply per minute = 11.70/60 = 0.19 lit/min.

Considering peak factor of 3 for this area this supply in peak hours will be = 0.19*3 = 0.57 lit/min.

Even during peak hours the one bucket of 15 Lit capacity will be filled with water in 15/0.57 = 26.32 min.

5.      Case V

In case of urban areas with 55 LPCD water supply for 24x7 supplies, days water supply for the household with 7 persons per house works out to 385 Lit/day.

If the supply is 24 hours then average hourly supply is 385/24 = 16.1 lit/hr.

If the supply is 24 hours then average supply per minute = 16.1/60 = 0.27 lit/min.

Considering peak factor of 3 for this area this supply in peak hours will be = 0.27*3 = 0.51 lit/min.

Even during peak hours the one bucket of 15 Lit capacity will be filled with water in 15/0.51 = 29.41 min.

1.      Case III

In case of urban areas with 70 LPCD water supply for 24x7 supplies, days water supply for the household with 7 persons per house works out to 490 Lit/day.

If the supply is 24 hours then average hourly supply is 490/24 = 20.41 lit/hr.

If the supply is 24 hours then average supply per minute = 20.41/60 = 0.34 lit/min.

Considering peak factor of 3 for this area this supply in peak hours will be = 0.34*3 = 1.02 lit/min.

Even during peak hours the one bucket of 15 Lit capacity will be filled with water in 15/1.02 = 14.71 min.

C.    Checking the pressure criteria

Lowest pressure criteria at the consumer end are 7 m. It can be assumed that the losses in the house connection and meter assembly are 1.5 m. And assuming the connection is at higher level as compared to the road level. Also presuming the effective head remaining at the consumer tap is about 3 m.

Assume connection size as 15 mm OD and 12 mm ID. Corresponding area is 0.000113 sq.m. Hence with pressure of 3 m on the tap velocity will work out to V= (2*9.81*3)^0.5 =7.67 m/sec.

Flow = 0.000113*7.67=0.000867 cum/sec =0.86 lit/sec = 52 lit/min.

Thus even for the lowest pressure flow is much more than the 24x7 flow requirements.

The bucket of 15 lit capacities will be filled in 17 sec.

Whole requirement 750 lit/day will be fulfilled in less than 15 min., if the pressure is maintained.

In case of other pressures for double story and triple story viz. 12 m and 17 m, similar calculations will show that if the pressure is maintained the systems will be more satisfactory systems.

D.    Consumer level of satisfaction

Consumer can be happy if he gets the water in required quantity as per norms reliably every day, at satisfactory pressures.

When a one bucket is getting filled consumer needs to wait.

Once the bucket is filled in he can take out that bucket and put the next bucket under the tap.

Consumer goes with filled bucket and empties it in the storage and gets back to the tap.

If he sees that the next bucket is filled, he is happy as he is not required to wait.

If the time lag for the consumer to come back and see the bucket is full is 1.5 min., then the 15 lit bucket is filled in 1.5 min., hence, the rate of flow is minimum 10 lit/min.

Following table gives the flow of water from the 12 mm dia. tap at various velocities and corresponding pressure range.

Dia. in mm	Dia. in m  D	Area in sq. mm	Velocity in m/sec	Flow in cum/sec	Flow in Lit/min.	V*V	(V*V/2g)= h in m
12	0.012	0.000113	0.1	0.01130	0.6782	0.01	0.0005
12	0.012	0.000113	0.2	0.02261	1.3565	0.04	0.0020
12	0.012	0.000113	0.3	0.03391	2.0347	0.09	0.0046
12	0.012	0.000113	0.4	0.04522	2.7130	0.16	0.0082
12	0.012	0.000113	0.5	0.05652	3.3912	0.25	0.0127
12	0.012	0.000113	0.6	0.06782	4.0694	0.36	0.0183
12	0.012	0.000113	0.7	0.07913	4.7477	0.49	0.0250
12	0.012	0.000113	0.8	0.09043	5.4259	0.64	0.0326
12	0.012	0.000113	0.9	0.10174	6.1042	0.81	0.0413
12	0.012	0.000113	1	0.11304	6.7824	1	0.0510
12	0.012	0.000113	1.1	0.12434	7.4606	1.21	0.0617
12	0.012	0.000113	1.2	0.13565	8.1389	1.44	0.0734
12	0.012	0.000113	1.3	0.14695	8.8171	1.69	0.0861
12	0.012	0.000113	1.4	0.15826	9.4954	1.96	0.0999
12	0.012	0.000113	1.5	0.16956	10.1736	2.25	0.1147
12	0.012	0.000113	1.6	0.18086	10.8518	2.56	0.1305
12	0.012	0.000113	1.7	0.19217	11.5301	2.89	0.1473
12	0.012	0.000113	1.8	0.20347	12.2083	3.24	0.1651
12	0.012	0.000113	1.9	0.21478	12.8866	3.61	0.1840
12	0.012	0.000113	2	0.22608	13.5648	4	0.2039
12	0.012	0.000113	2.1	0.23738	14.2430	4.41	0.2248
12	0.012	0.000113	2.2	0.24869	14.9213	4.84	0.2467

Hence, as for as the flow is concerned the level of satisfaction for the consumer is 10 lit per min. corresponding duration expected by the consumer to complete the total water supply in a day will be 75 min or 1 hour 15 min.

In case of urban and rural areas if the pressures are maintained in such a way that he 15 lit bucket will be filled in 1.5 min. then required water supply will be given in durations as mentioned in the following table,

Area	House hold size	LPCD	Demand in lit/day	Supply in lit/min.	Requirement of supply in min./day	Requirement of supply in hours /day
Urban	5	70	350	10	35	0.58
Urban	5	135	675	10	68	1.13
Urban	5	150	750	10	75	1.25
Rural	7	40	280	10	28	0.47
Rural	7	55	385	10	39	0.64
Rural	7	70	490	10	49	0.82
Rural	7	100	700	10	70	1.17

Thus in both the cases of Urban and rural areas requirement of water can be fulfilled in less than 1.5 hours considering all sorts of cases, provided pressures are maintained in such a way that the supply can be ensured at 10 lit per min.

Then why there is an insistence on 24x7 water supply. It does mean that consumer can, at his will utilize the services of water supply at any 0.58 hours to 1.17 hour duration to meet out his demand. He expects that the system shall run 24x7, and supply 24x7.

Thus it can be seen that 24x7 can have different interpretation.

E.     Interpret 24x7

24x7 water supplies has following shaded areas,

·         Water supplied is not directly addressed to demand of the consumer. There can be intermediate storage, either in the form of small tanks in the ground level or in the form of small tank on the top floors. These introduce the discontinuity with the supply and demand. Hence, demand pattern does not co-relate with supply. Naturally the demand peaks are subsided in the storages and the consumer is happy, if the supply is available to him even through the local storage. Peak factors are not transferred to the supply levels but they are balanced in the interim storages, but there are bulk stretches to have the local storages filled in.

·         In case of low cost housing areas and the slums the demand is directly stretched to the supplies for the ESR.

·         Consumer demand is not continuous with fluctuating rates, in 24 hours. Hence, the multiplications of demands, with the population are not a reality.

·         It is not the flow or pressure, but the most important is the reliability of service level at any time is the requirement.

·         Distribution system is the tool and the system is more important to impart the reliability.

Hence, it is to emphasize that the reliability of the system up to ESR, where, there is a hydraulic discontinuity, shall be most reliable system and shall have the potential to work for 24 hours, from where the distribution can draw the required water by consumer at any time of the day.

This is called 24x7 supplies.

F.      Requirements for the 24x7 supplies

·         Sufficient overall storages, say up to 33% to 40%.

·         Every storage/ESR shall have the influence area and it is proportional to the height of ESR.

·         Every ESR shall have identified DMA and inter DMA connections shall be prohibited.

·         Every ESR shall have the influence population within the DMA and demand can be worked out by knowing the population density.

·         All ESRs shall be having system of multi-outlets, so as to ensure the each sub DMA shall be having a maximum population of 15000 souls.

·         Each ESR shall have an influence zone of 1.5 to 2.0 sq.km area

·         Stretching the lines beyond influence zones will not be feasible.

·         Distribution system outlets shall be controlled and in any case the maximum 5 threads near ESR need to be opened.

·         It is the pressure that is important in the distribution system and flow will be available whenever required.

·         In any case the ESR water level shall not go below LSL.

·         Overflows shall have controls.

·         Distribution pressure optimization can be done by use PRVs or master pieces.

·         It will need more water for 24x7 initially and it shall be financially controlled when the consumer reacts to the bill. Till then the overconsumption shall be sustained. Hence, it is better to think 24x7 from part areas and not for full city.

·         24x7 will be eased out with meterization, but not 100% obligatory. It mainly depends on the billing system.

Then it is 24x7.

G.    Water supply status at consumer level

Cities trying for the 24x7, need to have the pre24x7 status conducive to the conversion. However, some cities are in such a stage that, they may be facing the problem of depressurization of the system along with intermittence in supply. City administration considers that the increase in supply, by operating the lines every alternate day will solve the problem. However, this does not help. Consumers try to get maximum supply from the pipe lines either by getting the supply in pits or they go further to use pumping direct to the pipe line during the supply hours. Even with supplying large quantity on the supply day consumer need to pump the water because of depressurization. Pressure gets reduced as each consumer is pumping directly from the line, in which the pipe line acts as a sump and while pumping, suction is created in the line using the positive pressure of the pipe line. Using such a system by number of consumers the system pressures go down rapidly.

It is interesting to point out a case study in Pune City.  Some observations were taken in the Vimannagar area, for the supply status. Sample meters were fixed on the consumer lines. Readings were taken for 15 days, in the supply hours. Quality of meter was very good. All the meters registered more than 350 LPCD water in duration of about 70 to 80 minutes of supply. Those consumers who did not use pumps had to worry about the supply. All others who afforded pumping had to go in for pumping to get the supply. As per hydraulic model this area was under less pressure as it is on the higher elevation and at farther end from the Elevated service reservoir.

Again assuming the consumer connection diameter of 15 mm. 350 LPCD in 80 minutes means 4.35 lit per min. And for a family actual flow was 4.35 * 5 = 21.75 lit per minute. This is definitely much more than the level of satisfaction. Naturally the consumers did not have any complaint.

Now, if such a supply is to be turned into 24x7, what is expected to be done? Consumers have already contributed for their level of satisfaction.

To change the service level to the level of satisfaction without using pumping practices is very difficult. Improvement of pressure in the system can be done by adding one common pumping station to boost the pressures in the system. Alternatively this can be done by adding one ESR nearer to this area. However, does not get convinced that he will get the supply with pressures. He may not have the patience to wait for 24 hour supply, as he is habituated to get the supply in 70 to 80 minutes. Pressures identified in the 24x7 supply system can be definitely less than the pressures he has been addicted to.

In such circumstances changing of consumer behavior is very difficult. Problem relates to consumer behavior and not setting of 24x7 supplies.

There is similar situation when the consumers prefer to go into pits for the benefit of the water supply in preference to the neighboring consumer. If we go along the line we find that the depth of the pit is increasing on upstream side. In such case, any improvement done in the pressures of the system will not be effective. Consumers will continue to get the water in the pits only. Only expected change can be that the consumer may have steps in the pit-taps, so that they can get the water at the higher level, instead of utensils getting drowned in the flown water. Out of fear consumer continues to get water in the pits. The phenomenon can be observed in the seasonal changes in the supply. In rainy season people get water at higher level, and consumer feels that he can get rid of some lift for lifting the bucket to above G.L.

In such cases the remedy is to dispense with pipe line as existing and lay the new line. Old pipe line might be having the holes from the bottom of the pipe line. They are not desirable nor they be easily plugged permanently. Once the new line is laid supply for the old line can be disconnected and the connections can be given from the new line. This being the improvement work in the system it shall be done with expenses borne by the scheme.

While changing the system by new lines another criterion is to lay pipe lines on both sides of the road, in the city. It is expected that the 100 mm line can contribute to 72 house connections of 15 mm dia. and it will give the satisfactory flows, if the pressures are maintained. For safety and for future expansion in the first stage it can be considered to have 50 No. of 15 mm dia. equivalent connections on one 100 mm line.

It is also necessary to decide the consumer line diameter for giving house connections and all the connections shall be restricted to be given on that diameter only. All above diameters pipe lines can be system lines.

H.    Deciding the consumer line diameter

Size of consumer line is dependent on the population of the city. It will calculate the no. of households. In the present stage there can be some percentage of households accommodated in the storied buildings. For calculating the population in storied buildings/apartments, a nominal survey of the group of consumers getting supply in the sumps in their premises and then pumping to the top level storages, needs to be done. A trend is needs to be anticipated for the future.

Secondly, if the city distribution is designed with 12 m or 17 m pressures, it can be assumed that the buildings upto two stories can be easily dealt with direct pressure. These decisions can be taken in the DMA wise also, for a bigger city. Consumer diameter can be different in the different DMAs.

In Maharashtra there are 26 Municipal Corporations and 221 Municipal Councils. For Corporations there can be separate detailed design for the distribution system. But as far as the Municipal Councils are concerned following analysis will help for the guidance.

Configuration of the Municipal councils is as following,

Sr. No.	No. of Municipal councils	Population range in 2011	Max. HH in 2011
1	23	Up to 15000	3000
2	16	15000 to 20000	4000
3	26	20000 to 25000	5000
4	24	25000 to 30000	6000
5	21	30000 to 35000	7000
6	22	35000 to 40000	8000
7	13	40000 to 45000	9000
8	13	45000 to 50000	10000
9	16	50000 to 60000	12000
10	11	60000 to70000	14000
11	12	70000 to 90000	18000
12	7	90000 to 100000	20000
13	11	100000 to 150000	30000
14	6	150000 to 300000	60000
	221

All these councils are expected to increase in their population by about 20% per decade. In Design stage of 30 years the population can be increased to 1.2*1.2*1.2 = 1.728 times the present range of population. Assuming also the household size will be 5 up to design stage. Further the target water supply shall be 750 lit per household and there can be about 25% losses in the distribution system. Hence, up to ESR household supply level will reach to 750*1.25 = 937.5 Lit per day.

Approximate design requirements of storages proposed in the Municipal Councils

Max. HH in 2011	Design HH in 2041	Demand at ESR	ESR cap. Required in ML	Cap. of each ESR in ML	No. of ESRs	Total Elevated storage in ML
3000	5184	4.86	1.62	0.50	3.00	1.50
4000	6912	6.48	2.16	0.75	3.00	2.25
5000	8640	8.10	2.70	1.00	3.00	3.00
6000	10368	9.72	3.24	1.00	4.00	4.00
7000	12096	11.34	3.78	1.00	4.00	4.00
8000	13824	12.96	4.32	1.00	4.00	4.00
9000	15552	14.58	4.86	1.50	3.00	4.50
10000	17280	16.20	5.40	1.50	4.00	6.00
12000	20736	19.44	6.48	1.50	4.00	6.00
14000	24192	22.68	7.56	2.00	4.00	8.00
18000	31104	29.16	9.72	2.00	5.00	10.00
20000	34560	32.40	10.80	2.50	4.00	10.00
30000	51840	48.60	16.20	2.50	6.00	15.00
60000	103680	97.20	32.40	2.50	13.00	32.50

Using multi-outlet system to the proposed ESRs we can calculate the configuration of outlets having distribution velocity as 1 m/sec. Outlet diameter can be given from the following table in which diameter of pipe and its carrying capacity in LPS is given with assumed velocity 1 m/sec.

Dia. of pipe in mm	Velocity in m/sec.	Carrying capacity of pipe in LPS
80	1 m/sec	5.0
100	1 m/sec	7.8
150	1 m/sec	17.6
200	1 m/sec	31.3
250	1 m/sec	48.8
300	1 m/sec	70.3
350	1 m/sec	95.7
400	1 m/sec	125.0
450	1 m/sec	158.2
500	1 m/sec	195.3

Guiding table for the ESR outlet diameters in mm and selection of Diameter of pipe in distribution system on which connection can be given

Max. HH in 2011	Design HH in 2041	No. of ESRs	HH per ESR	No. of outlets	Flow in LPS through each outlet	Dia. of Each outlet or stem dia. in mm	Max. dia. on which connections can be given in mm
3000	5184	3.00	1728.00	2.00	22.50	150.00	100
4000	6912	3.00	2304.00	2.00	30.00	150.00	100
5000	8640	3.00	2880.00	2.00	37.50	200.00	100
6000	10368	4.00	2592.00	2.00	33.75	200.00	100
7000	12096	4.00	3024.00	3.00	26.25	150.00	100
8000	13824	4.00	3456.00	3.00	30.00	150.00	100
9000	15552	3.00	5184.00	2.00	67.50	250.00	100
10000	17280	4.00	4320.00	2.00	56.25	250.00	100
12000	20736	4.00	5184.00	2.00	67.50	250.00	100
14000	24192	4.00	6048.00	2.00	78.75	300.00	100
18000	31104	5.00	6220.80	2.00	81.00	300.00	100
20000	34560	4.00	8640.00	3.00	75.00	300.00	100
30000	51840	6.00	8640.00	3.00	75.00	300.00	100
60000	103680	13.00	7975.38	3.00	69.23	250.00	100

Considering the future developments it can be better practice to have consumer service lines shall be on both sides of the roads at least in cities having population more than 30000 as per 2011 census population.

Similar calculation can be made for the various Corporations. It can be found that the consumer service line diameter can increase to 150 mm.

All the consumer service lines need not be designed. However, they shall be laid in addition to the design lines to be laid on the same road. It shall be ensured that the pressures at any point at the end of service line shall be design pressure.

In big cities it is not necessary to design distribution with more than minimum pressure of 7 m, as practically all the properties can be having the sump and pump house. This can allow about 18 m pressure loss in the distribution system, from ESR to Consumer service line. Pressure optimization can be done by PRVs.