Building redevelopment: Water storage and pump system

Scenario

The main obstacles to consider were head height and existing services pipe & cable tray as the tank was to be located in the underground car park.

Solution: To provide a 14,550 litre sealed storage GRP tank with open drywell pumps mounted externally to accommodate service and maintenance.

The tank capacity and pump flow rates were calculated from occupancy for design as 194 persons for 12 hours per day at 75 Litres/person = 14550 Litres.

2 x Flygt N type drywell submersible pumps to be mounted externally to the tank complete with mounting/installation kits.                                                                                                                                  Pumps will have open self-cleaning channel impeller 3-phase motor The proposed duty is 19l/s. 

The pumps are to be controlled via a dual controller with auto changeover and the level maintained by an ultrasonic level controller. A back-up float is installed in the tank to bring a pump into service should the ultrasonic controller loose the echo for any reason. The new pipework would be connected to the existing time saver discharge pipe which runs to gravity into the main sewer.

The 55mtr pipe run had to be adapted to overcome the many existing services both mechanical and electrical and had to remain higher than any of the lowest protrusions and not reduce the access into the parking bays. The new ductile iron pipework had to be connected to the existing 100mm timesaver foul waste pipe which was done by utilising an 80mm-100mm flanged pipe spigot and a 100mm flex-lock coupler. A remote alarm panel was installed into the security office and linked to the control panel to provide alarm indication in a manned area.

 Outcome: A service contract has been set up to provide 2 visits per year:

Visit 1:

• Minor Service
• Incorporates a visual inspection and test operation of pumps and control panel

Visit 2:

• Major Service
• Incorporates a de-sludge of the tank with the use of a vacuum tanker
• Check & clean the ultrasonic level transducer and floats
• Remove the pumps from the volutes and check impeller/volute conditions, bearing condition, electrical tests, refit, and carry out operational checks.
• Test alarm operation
• Test operation of isolation and non-return valves
• Reinstate back into auto operation