5
Water Services Trust Fund
Construction Manual for a Yard Tap
INTRODUCTION
This structure consists of a 1200 x 800mm rectangular concrete fetching bay and drainage porch cast above the ground with 75mm high concrete kerbs on three adjacent sides to contain spilt water. The kerbs are cast above a 150mm thick concrete platform. The fetching bay is laid to fall at a slope of 1/200 toward a grooved concrete porch (drainage surface) and a drain with a 200mm diameter floor trap. The drain channels the spilt water towards the soak away pit.
The yard tap is positioned at corner of the fetching bay as shown in the yard tap drawings. The pipe supporting the tap is about 1250mm above the ground. Refer to the yard tap drawings for a clearer illustration on where the tap will be positioned.
All the concrete surfaces are reinforced with wire mesh for strength and stability. To maintain a dry surrounding of the yard tap area, there is a 500mm perimeter of ballast (coarse aggregates) sprung around the concrete zone of the yard tap.
The following items are required for on-site construction of the yard tap:
a) Hardcore; 3 Ton.
b) Quarry dust (murram); 2 Ton.
c) Ordinary Portland cement (50 kg. bags); 3No.
d) Building sand; 2Ton.
e) Ballast; 3 Ton.
f) 150 x 25 mm formwork timber; 5m long
g) Binding wire; 1.5 Kg.
h) Fabric mesh; 2m2 BRC A 142.
i) Wheelbarrow; 1No.
j) Excavation & hand tools like hoes, shovels, hammers, pegs, measuring tapes, mixing bowls, etc. and other tools recommended by the engineer.
k) 100mm heavy duty PVC waste pipe.
l) Galvanized iron pipe class B (per 6 metres); 2No.
m) Gate valve (pegler); 1No.
n) Water meter; 1No.
o) Heavy duty taps; 1No.
p) Union; 1No.
q) Bend; 1No.
r) Nipples; 4No.
s) 200mm diameter floor trap.
t) 450 X 450 X 50mm concrete GT covers; the number to be determined on site.
PRELIMINARY PREPARATIONS
§ Acquire the site; set aside a minimum area of 1500 x 1200mm for the construction.
§ Clear the site of all vegetation, solid wastes, etc.
§ Excavate the top soil on the whole site to a maximum depth of 150mm, depending on the soil conditions.
§ Cart away all excavated material to an authorized dump site.
§ Gather to site all the construction tools needed and allocate a space for their storage.
§ Mark out the route for the supply pipeline from the mains and the drainage route prior to setting up the kiosk. Peg and measure the actual distances by tape.
§ Excavate the trenches for the above mentioned pipes at a depth to be determined on site and to the approval of the engineer.
§ Provide a 1:4:8 concrete mix blinding for the foundation footing for laying the pipes.
§ Lay the supply pipeline, backfill the laid sections and install all the pipe fittings (valves, valve chambers etc.).
§ Ensure that a substantial length of the pipe is left jutting out above the ground surface to give an indication of where to cast the concrete mix for the fetching bay and drainage area. The length of this external pipe is 1200mm.
§ Excavate an area of 1200 x 800mm to a depth of 200mm and backfill with hand packed and well compacted hardcore.
§ Spread a 25mm thick murram blinding above the hardcore layer.
A. GROOVE TEXTURED DRAINAGE PORCH
This is a concrete landing at the front face of the fetching bay and the tap. Refer to the drawings to get the exact position. It provides the main access to the yard tap and an area where buckets or jerricans can be placed by people queuing for water. It also supports the adjoining edge of the fetching bay, and is the first precast panel to be positioned on the ground.
§ Locate and mark the positions of where to lay the terrace. Hammer four pegs to indicate the exact position of the corners of the terrace panel.
§ Position the timber formwork around the 1200 x 800mm area and fix the fabric mesh above the ground using iron hoops.
§ Provide a 1:2:4 concrete mix for casting this drainage surface. Mix well and pour over the fabric mesh, smoothen the surface, serrate the area of the 25mm drainage grooves using a smooth edge of timber and leave the concrete to set for 3 days. Reinforcement of the concrete slab should be carried out under the supervision of an engineer.
§ Sprinkle water on the concrete surface twice a day to ensure the concrete sets with no cracks and protect the surface from moisture loss by lining with a layer of polythene sheet.
§ Remove the pegs and formwork once the porch has set.
§ Fix the 200mm diameter floor trap in position above the drain as shown in the drawing.
B. FETCHING BAY
This comprises a 150mm thick platform with adjacent 3No. 75mm high concrete kerbs above it. It is the elevated part of the yard tap area where a bucket would be placed when fetching water. It measures 600 x 800mm.
§ Locate and mark the positions of where to lay the fetching bay using pegs.
§ Position the timber formwork around the area where the fetching bay and kerbs will be cast and position the fabric mesh above the already set drainage porch using iron hoops.
§ Provide a 1:2:4 concrete mixes for casting this fetching bay and kerbs. Mix well and pour over the fabric mesh, smoothen the surface and leave the concrete to set for 3 days. Follow the same procedure for the concrete kerbs. Refer to the drawings to get the actual dimensions.
§ Sprinkle water on the concrete surface twice a day to ensure the concrete sets with no cracks. Protect the concrete surface from moisture loss using a layer of polythene sheet.
§ Remove the formwork and polythene sheet once this unit has set.
C. YARD TAP
§ Assemble sequentially all the piping and fittings for the yard tap as per the engineer’s approval. Refer to the drawing for this.
§ Test-run the pipe and fixtures to check the system for pressure and leakages.
D. PLUMBING WORKS
§ Fix the drain as shown in the drawing at a slope not exceeding 1/200.
§ Site the soak away pit and drainage pit pipe routes. Mark the exact positions.
§ Excavate the pit and trench to a minimum depth of 500mm and also to suit the prevailing site conditions.
§ Build the inner soak away walls by placing the selected stones in the soak away as per the details in the drainage drawings and to the engineer’s approval.
§ Cast the drains as mass concrete and provide a 450 x 450 x 50mm concrete GT cover as per the drawings and to the engineer’s approval.
§ Construct the inspection chamber and soak away pit cover.
§ Lay the drainage pipes at the gradient shown in the drawing (min. 1/200).
§ Clean up the site once construction is complete.
If You Need More Information
If you have any questions, observations or suggestions regarding this construction manual for yard taps or concerning the yard tap itself, please do not hesitate to contact the Water Services Trust Fund. [1]
Address: CIC Plaza, 1st Floor, Mara Road
P.O. Box 49699 – 00100,
Nairobi, Kenya
Tel: +254 – (0)20-2720696
+254 – (0)715-732199
E-mail:
Website: www.wstfkenya.org
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Toolkit for Urban Water Supply Projects Module 6 Construction Manual for Yard Taps
[1] This Construction Manual was developed by John Orwa, and Eden Mati.