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Dirt Box & Water Meter: Correct Procedure, Implications: Some Questions

I find at a number of pumping installations, the dirt box and the water meters are coupled together and installed. 

The water meter manufacturers specify a requirement of straight pipe of 10 times the diameter of the meter both upstream and downstream.  They also recommend installation of a dirt box (Strainer) upstream of the water meter for protection of the meter impeller. 

In many of the installations in our pump houses I find the dirt box and meter are joined together through a common flange and installed.  In the case of dirt box, the water passes through the strainer through a curved path.  The area of cross section also varies.  I want to know whether the 10d straight pipe has to be installed in between the dirt box and the water meter. And what are the implications of the same?

P. Gopalakrishnan

pgopalakrishnan@mail.twadboard.gov.in

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Comments

1.

Dear Gopalakrishnan,

The practice of joining the strainer and meter is flawed. This is because during straining of solids, there is disturbance in the water path and sometimes, this gives an incorrect reading in meters. Over 10 times diameter, the flow tends to stabilize itself. The other reason is having water meter immediately after strainer creates further turbulence in water flow which may result in decrease in strainer efficiency and there may actually be a slippage of dirt through it.

The water department follows the incorrect practice because the water meter box is very small and if they were to follow the correct practice, they shall have to provide a large box of 1 ft x 2ft or two boxes of 1ft x 1ft. But you know there is no one to govern over the government.

With best regards,

Taral Kumar
Executive Director
Akar Impex Pvt. Ltd.
E-9, Sector 6, Noida
Uttar Pradesh

2.

Dear P. Gopalakrishnan,

Please refer Chapter 12 “Water Meters, Instrumentation, Telemetry & Supervisory Control and Data Acquisition (SCADA) of Manual on Operation and Maintenance of Water Supply System Published by this Ministry of Urban Development in January 2005.

For access to this please see the web site:
www.urbanindia.nic.in
www.cpheeo.nic.in

Regards,

Mangalam Sankaranarayanan
Deputy Adviser
The Central Public Health and Environmental Engineering Organisation (CPHEEO) Ministry of Urban Development
Government of India

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