South of England Large Prestigious Government Site

The Background:
This prestigious government site is one of the largest in the South of England. Spanning across 2,500 acres, the site was primarily built to provide a high-standard, permanent accommodation. The site recently underwent an extensive regeneration programme, by refurbishing all existing buildings and building new, the total site now consists of 160 separate buildings, and it is now home to more than 12,000 residents. Across the entire site, there are approximately 1,500-2,000 cold-water storage tanks installed, which service the entire site.

The Challenge:
The cold-water storage tanks at the site had been installed like most cold-water storage tanks found out in the field, typically configured with either a division or as two separate tanks. The rationale for typically installing cold-water tanks in this way is to enable maintenance to be easily carried out and/or to allow the ability to clean and chlorinate the tanks as and when required, whilst leaving an uninterrupted water supply to the buildings.

However, installing cold-water storage tanks in this way can sometimes lead to a tank imbalance and stagnation issues on one side of the tank. If one float valve is favoured over the other, or if one valve activates and keeps pace with demand, it will backfill into the other side. When this happens, a biofilm can form, which then quickly becomes an ideal breeding environment for waterborne bacteria. This situation can present itself irrespective of the type of valve installed.

This very issue was continually being experienced, and therefore, the site decided to approach Keraflo for their expert advice on a tank with a division that had two Equilibrium Valves, where a biofilm had formed in one compartment.

The Solution:
After conducting a full site survey, Keraflo were very confident that the issue could be easily and quickly resolved; Keraflo presented two unique solutions for the team to consider.

The first was to integrate a Keraflo KP Twin Float Valve Kit, which has been specifically designed for a twin/portioned tank. This solution uses a KB delayed action pilot valve, which are installed in each separate tank or division. As the water level drops, whichever pilot valve opens first, will then activate the main control valve. This then triggers simultaneous filling in both sides of the tank, offering the flexibility of closing off one tank or division, while leaving the other side in full service.

The second solution, which Keraflo recommended, was Tanktronic. This electronic tank management system uses a sensor in each tank compartment to provide a constant readout of the water level, volume, and temperature in both sides of the tank, which is displayed on the control panel. It can also fill the tanks through several valve options.

For the site, the Keraflo Servo Ceramic Valve (SCV) were proposed as Tanktronic can activate both valves simultaneously, preventing biofilms from forming, but still allowing the flexibility to operate independently when cleaning, chlorination, and maintenance is required. The additional benefit of installing Tanktronic is that the system also allows for the water levels to be adjusted from outside of the tank, or even automated using the calendar function, providing greater control to meet the site’s unique requirements. This allowed the site to vary their water levels dependant on the time of day/week/month/year, thereby matching capacity to demand. This was a key requirement for the site.

In addition, Tanktronic also provides two stage alarms for high and low water level and temperature. These alarms display on the Tanktronic panel and can also be sent to the BMS or third-party devices, such as a low-level booster-set interlock.

After carefully considering both solutions, a Tanktronic field trial was commissioned in a tank with a central division to fully demonstrate the true capabilities of Tanktronic. The site particularly favoured the idea of utilising the calendar function, so they could drop the water level weekly if required to ensure the water in the tank was completely turned over when occupancy was low.

The pictures below show a tank with a division installed at the site. Originally, there had been a 1½” Equilibrium installed in each side of the tank, and the left hand side of the tank is being favoured over the right, so much so that a biofilm has formed on the right.

Conclusion:
Immediately after Tanktronic was installed and commissioned, the biofilm completely disappeared, successfully demonstrating that the solution was capable of effectively resolving the issue for the site.

Client Testimonial:

“Over the last 12 months, we have worked very closely with Keraflo to help us understand how we can prevent biofilm from forming in our cold-water storage tanks. The 2-month long trial which was commissioned, clearly demonstrated how by integrating the Tanktronic solution not only provides us with the confidence that the water in the tank is continually turned over, to avoid stagnation, it also provides intelligence on the condition of the water, alerting us to any variances that may require quick remedial intervention. This means our policy is to now only clean and chlorinate “when alerted,” in addition to adopting the annual clean and chlorinate best practice.
This has significantly reduced the time spent cleaning and chlorinating the tanks, as biofilms are no longer forming, we also have reduced the substantial volumes of chemicals we used for each clean to treat the tanks. Given the success of the trial, we will look to roll out the same solution into other tanks across our site in the future.”

Technical Manager at the site.