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    The Best Way to Dewater New Transformer Bunds

    There are a variety of systems for transformer bund drainage. Some scenarios call for sophisticated monitoring and pumping systems but these increase the complexity and cost of bund construction and introduce multiple points of failure. For lower-risk sites, this may be overkill.

    In this article we look at a low-cost, low-maintenance and scalable solution which offers an alternative to oil-discriminating pumps, oil water separators and vacuum tankering.

    DrainEezy Bund Filters attach to a simple drainage outflow built into the transformer bund.

    Oil is removed from the bund water as it passes through the filter, allowing clean water (less than 5ppm oil) to be discharged to surface drains or the environment.

    Popular with transformer manufacturers and maintenance contractors, these filters are simple and highly effective.

    Here are five reasons why DrainEezy Bund Filters could be the best solution for your transformer bund installations.

    Reduced construction costs

    Installing oil discriminating pumps and underground oil water separators can add a week to bund construction. Additional costs include specialist equipment, an electrician to wire, test and certify equipment, and oversight by a senior authorized person (SAP).

    Retrofits may require the transformer to be switched off and the load transferred. With more third-party operatives on site, your health and safety risks are also higher.

    DrainEezy Bund Filters simply require a drainage outflow to be built into the bund.

    High performance

    Water enters the filter from the bund outflow and passes through a hydrocarbon filter. Clean water is discharged from the filter into the environment.

    Filters are available with a range of capacities and flow rates. They are designed to allow bunds to drain quicker than they can fill. On low-risk sites, filters may last years before needing to be replaced.

    The active component in these filters is a proprietary smart polymer which reacts with the transformer oil to form a solid and insoluble rubber-like substance. Trapped inside the filter, the solidified oil physically can’t leak out. (Watch how our smart polymer solidifies oil here.)

    When all the polymer in the filter has been activated by oil, flow is naturally blocked so no leakage can occur. This means that the filters deliver a failsafe response in the event of a catastrophic breach.

    Low maintenance

    DrainEezy bund filters have no mechanical parts or power requirement which reduces the potential points of failure. This is ideal for remote and infrequently-visited locations.

    Your regular maintenance engineers simply to need to check the filters when on site. An accumulation of water in the bund indicates either that the filter needs cleaning out or replacing.

    A fitting kit enables the filter to be removed, inspected and replaced without any leakage occurring.

    The smart polymer inside the filter poses no health and safety issues to maintenance operatives and units can be disposed of in standard hazardous waste bins.


    As a transformer ages and the rate of leakage increases, lower-capacity filters can be replaced with higher-capacity units, or additional filters can be added to a bund.

    Similarly, filters can be retrofitted to bunds to replace or provide support for pumping systems that are struggling to perform.

    Low cost

    Filters are very low cost. Factor in the savings on construction, installation, maintenance and waste oil/water removal, and DrainEezy Bund Filters offer a very cost-efficient solution.


    Bund Filters aren’t suitable for every situation. Old transformers leaking litres of oil each day would quickly overwhelm a filter and instead require substantial preventative measures.

    For new and smaller transformers, however, DrainEezy bund filters offer considerable advantages.

    To request a quotation, please call us on 01206 299388 or email

    For more information, see DrainEezy Bund Filters.

    Filters can also be provided in single and multi-filter chambers, to manage the outflow from a series of bunds or a site. (Ask too about our creosote filters for utility pole and sleeper depots.)