WATER & WASTEWATER ENGINEERING Water Supply Engineering Lecture No. 4 Water distribution system

Water distribution system E.T From R.S.F G.T HLP 1- Pump station (HLP) 2- Storage (ground-elevated) 3- Pipe network

Water distribution system Storage system: What is the purpose of storage system? With regard to water quantity 1.Storage for change in quantity of water demand. 2.Emergency storage (6-8 h) 3.Fire demand 1/5 fire demand storage by elevated tank 4/5 fire demand storage by ground tank

Water distribution system With regard to water pressure 1. For elevated tank near pump station: a)Fix the head on pumps, then they work at max. efficiency of pump b)Prevent water hammer 2. For elevated tank in middle town: Give better distribution for head pressure 3. For elevated tank at distant point: Improve the head at distant point Improve the head for extension

Water distribution system Design of Elevated tank: 5 4 supply b b a+b b empty b 3 a demand 1 time

Water distribution system المماس للمنحني اكبر من ميل الخط ( ال supply ) يحدث تفريغ للخزان المماس للمنحني اصغرمن ميل الخط ( ال supply ) يحدث ملئ للخزان Capacity c1= [(a+b)/1000]*pop*1.5 C3 (fire) = 0.2* w.c/h *pop/10000

Water distribution system Depth =6-10 m D 0 > 35m Di = (2-3)m capacity of one tank less than or = 2000 m 3 c= n ∏/4 * (D 0 - Di) depth

Water distribution system Design of HLP H P = γ × Q max × H t 75 × η 1 × η 2 Q max = 1.8 Q av. + Q fire Q av. = W.C* pop Q fire = w.c /h* pop/10000 η 1 =0.7 η 2 = 0.9

Water distribution system Basic requirements Network types, accessories network design  pipe equivelent  method of selection  Hardy cross method  Computer analysis

Water distribution system Basic requirements (minimum requirement) هي عبارة عن ضمان لكي تكون هذه الشبكة ذات كفاءة تشغيل عالية 1- well laid pipe Served city Water network covering the city

Water distribution system Pipe material هي عملية اختيار انواع المواسير التي سيتم استخدامها في تصنيع المواسير و ذلك بعد التعرف علي خصائص الجسات التي تؤخذ للتربة كل حوالي 100 متر. GCI GRP DCI STEEL RC HDPE UPVC PP

Water distribution system 2- Pressure of discharge It is the quantity of flow that we will need to face our needs. يجب علي الاقل من توفر ضغط يعادل 25 متر.

Water distribution system 3- Network types A- tree system يمكن استخدامها علي نطاق صغير في الاماكن المحدودة. P.S

Water distribution system من عيوبه : انقطاع المياه عن المدينة عند حدوث اي كسر في الخط الرئيسي. وجود ال dead end مما يعمل علي نمو الطحالب عند النهايات بالإضافة الي حدوث مشكلة المطرقة المائية نتيجة ارتداد المياه عكس اتجاه السريان مما يعمل علي كسر ريش الطلمبات.

Water distribution system B- Grid iron loop )dead ends( هي عملية ربط ال ( في النوع السابق مع بعضها P.S نحاول ان نعمل كوردون حول المدينة ككل ثم يتم تقسيم هذا الكوردون الي اقسام صغيرة.

Water distribution system من مميزاتها : التغلب علي مشكلة انقطاع المياه في المدينة كلها عند حدوث كسر في الخط الرئيسي. عدم وجود ال dead end عيوبها : ذو تكلفة عالية

Water distribution system Main distribution system: ᶲ min =300 mm for big cities = 250 mm for cities and big towns = 200 mm for towns = 150 mm for villages No. of valves = (n-1) where n is the number of main feeder Minor system: ᶲ min= 100 mm No. of valves = (n-2) where n is the number of secondary feeder

Water distribution system  So The basic requirements of network: 1- well laid pipe of durable material 2- sufficient capacity to meet max. demand at any time. 3- absence of dead ends Grid-iron 4-more than one feeder

Water distribution system Network Accessories:  E.T ( we must choose the location of E.T so that to avoid many problems such as water hummer) sluice gate pressure relief valve  Valves non return valve or check valve float valve air relief valve wash out valve

Water distribution system 1.Sluice valve It is used to control the flow of water in distribution system during repairs and maintenance Adv. Cheap in construction low resistance to the flow of water

Water distribution system Pressure valve It is used to relief high pressure in pipe line automatically and which is caused by sudden closing of gate valve. It is used to prevent water hammer float valve Used in reservoirs (automatically)

Water distribution system Non return valve or check valve It is an automatic valve which allow water to flow in one direction It is used at elevated tanks, pumping stations Air relief valve It is used in long pipe lines, air accumulates at high points and will interfere with flow of water and increase velocity and friction This valve allow air to escape to atmosphere

Water distribution system Wash out valves It is provided at lowest point and dead ends to drain out waste water or sediment that may be collected This valve must be in a chamber

Water distribution system Hydrants 1.Fire hydrant (on minor only) They are provided at all street crossing and turning at distance m 2. Irrigation hydrant Like fire hydrant

Water distribution system Design of pipes networks Four parameters must be computed for any pipe of the network for purpose of complete analysis, they are: 1.Slope of HGL along the pipe“S” It is the head lost per unit length of pipe 2.Velocity of flow inside the pipe ‘V’ m/s 3. Diameter of the pipe ᶲ mm 4. Rate of discharge in the pipe Q l/sec

Water distribution system Hazen & Williams formula V= C D 0.63 S 0.54 V = The mean velocity (m/sec) C= Hazen & Williams friction factor D= internal diameter (m) S = HGL

Water distribution system Methods of distribution system analysis: 1.Equivalent pipe method 2.Method of sections 3.The circle method 4.Hardy-cross method 5.Computer analysis

Water distribution system 1.Equivalent pipe a.Pipes in series H Q Q1 Q2 Q3 D1,L1 D2,L2 D3,L3 Q = Q1 = Q2 = Q3 H= H1 + H2 +H3

Water distribution system TO DETERMINE THE EQ. PIPE Assume Leq Then find Seq = H (cm) / Leq (m) *100 From chart get Deq. OR Assume Deq. From chart get Seq., Then find Leq. = H (cm)/ Seq( cm/100m)*100 = m

Water distribution system b. Pipes in parallel Q1,L1,D1 H Q Q2,L2,D2 Q3,L3,D3 Q=Q1+Q2+Q3 H=H1=H2=H3

Water distribution system 2. Method of sections هذه الطريقة تستخدم بعد حساب اقطار الشبكة و ذلك للتاكد من الحسابات و كفاءة الشبكة خطوات التصميم : 1. حساب القطر لكل ماسورة تقريبا عن طريق حساب المسافة المخدومة بكل ماسورة 2. يتم اخذ مقطع بحيث يكون عمودي علي اتجاه محصلة ال flow في الشبكة 3. لكل مقطع يتم عد المواسير مع اهمال الاقطار اقل من 6” في المدن 4. يتم حساب ال Q لكل ماسورة من الذين تم قطعهم و ذلك باخذ C= 100, HL = 2m/Km 5. يتم حساب Q1 Q1=SUMM OF FLOW IN CUT PIPES يتم حساب Q2 Q2= WATER DEMAND FOR THE DOWNSTREAM AREAS OF THE CITY Q2= DOMESTIC DEMAND + FIRE DEMAND

Water distribution system Domestic demand= pop*Qav./(24*60*60) = L/sec Pop = area of D.S the section *pop denisty = عدد السكان الكلي * ( عدد المربعات خلف القطاع / عدد المربعات الكلي )

Water distribution system Fire demand popFire demand L/SEC

Water distribution system Ground reservoir Purpose of ground reservoir 1.Cover the contact time for disinfection [cl 2 (0.5- 1hr)] 2.Cover the emergency requirements 3.Cover the difference between Qmax daily &Qmax monthly 4.Cover 80 % fire demand

Water distribution system The reservoir is laid under ground 1.To keep the temperature of water 2.To decrease the construction requirements 3.Not to high the constructions before the reservoir Importance of the internal walls 1.To stir the water from the inlet to the outlet to be sure of the disinfection process to kill the bacteria in a certain time 2.To decrease the area of the slab to be designed as one way slab

Water distribution system Importance of the air vent To ventilate the water Help in emptying the reservoir Help in filling the reservoir give alarm in case of stopping the float valve

Water distribution system Design criteria Capacity C 1 =(1/2-1)hr * Q mm disinfection C 2 = Q mm * T(4-10)hr emergency C 3 = (Q m.d – Q mm *1d) difference between max consumption & max production C 4 = 0.8*120*pop/ % fire C d =the max of C 1,C 2,C 3 + C 4 = hLBd

Water distribution system d= 3-5 m Area > 2000 m 2 L= K*5m = ( )B > 50 m n < 2 (n عدد الخزانات ) Notes Fire demand Fire hydrant flow = 60 m 3 /hr Fire duration = 2 hrs C 120 m 3 fire = 120*pop/10000 (m 3 ) if given fire demand =6000 m 3 C 4 = 0.8*6000 m 3 emergency = 25 % of the summer flow (Q mm ) C 2 = 0.25 Q mm