During 2020, a £1.3m refurbishment was given to the 25m four lane swimming pool at Ongar Leisure Centre in Chipping Ongar, Essex. The project aimed to upgrade the pool plant and plant room, add LED lighting and extend its life by around seven years. The Mechanical & Electrical Engineers for the project was Balm and Davies who, in November 2020, sub-contracted the replacement of the pool plant to Sterling, who were given the responsibility of increasing energy efficiency and reducing maintenance costs.

Ongar Leisure Centre is operated by Places Leisure on behalf of the Local Authority, Epping Forest District Council.

The new system required a bulk sodium hypochlorite storage tank for disinfection.

Project Brief - Analysing the health of the plant and identifying upgrade options

The overall aim of the project was to increase energy efficiency and reduce maintenance costs. On inspection, Sterling found that the existing steel filter vessels, circulation pumps and pipework in the plant room were beyond economical repair and would need to be replaced, although the existing plate heat exchanger was in good condition and was retained.

The new system required a new Category 5 raw water feed tank and booster pump set to comply with the water company’s regulations, a new bulk sodium hypochlorite storage tank for disinfection, a hydrochloric acid dosing system for pH correction and new polyaluminium chloride dosing system using a Flocdos dosing pump to provide coagulation of particles and removal of Cryptosporidium. The existing Ezetrol chemical dosing controller was in good condition and was retained.

Filtration of the circulating water is provided by two SLX filters with five-valve frontal pipework manifolds, side access manways and a sight glass.

Energy Efficient Plant

The new plant was based on turning over the pool volume in three hours at 157m3/h using three new 5.5kW circulation pumps operating as duty/duty/standby. The flow is reduced for eight hours overnight to 146m3/h. A new motor control centre, fitted with inverter drives, was installed to manage the pump operation with flow monitoring via a new electromagnetic flow meter in the new circulation pipework. The use of inverter drives reduces the power consumption of the 5.5kW pumps of around 25,000kWh per year by comparison with the original system.

Filtration of the circulating water is provided by two SLX filters with five-valve frontal pipework manifolds, side access manways and a sight glass. These operate at a service rate of less than 25m3m2h-1 velocity through the filters, both in line with PWTAGs recommendations. Removing the old steel filter vessels and installation of the new GRP filters was difficult due to the restricted access to the plant room, but was accomplished by Sterling’s in-house specialist installation team, working in close co-operation with the Mechanical & Electrical Contractor.

The existing Ezetrol chemical dosing controller now controls the new sodium hypochlorite and hydrochloric acid systems, both of which are fitted with “dead man’s” switches to prevent overfilling of the day tanks. The polyaluminium chloride dosing pump is flow paced against the signal from the new electromagnetic flow meter.

The new plant was based on turning over the pool volume in three hours at 157m3/h using three new 5.5kW circulation pumps operating as duty/duty/standby.

Success for Sterling

“Although access into the plant room was very restricted, the new plant was installed without any problems”, says Balm and Davies Contract Manager, Dennis Parker. “The works were completed on schedule.” The Ongar Leisure Centre upgrade project was a complete success with the new plant achieving the anticipated energy savings.

Although access into the plant room was very restricted, the new plant was installed without any problems

— Balm and Davies Contract Manager, Dennis Parker