Complii has acquired GMS Services Limited, a UK provider of water hygiene, water treatment and mechanical services. The transaction expands Complii’s Water division across the Midlands and northern England.
GMS Services is headquartered in Wigan and has an operational base in the Midlands. The company works nationally across housing, local government, healthcare and education, including multi-site customer contracts.
GMS adds water hygiene and Legionella expertise
GMS Services provides Legionella risk assessments, water hygiene monitoring and testing, thermostatic mixing valve maintenance, tank inspections, cleaning, disinfection and chlorination. The company says it has delivered water safety services since 1997.
Its services cover the assessment, monitoring and management of risks within building water systems. GMS also provides water treatment, mains pipe chlorination, training and compliance-management services.
The acquisition gives Complii additional capacity in a market governed by health and safety duties for employers, landlords and others responsible for premises. The UK Health and Safety Executive requires dutyholders to identify, assess and manage potential exposure to Legionella bacteria.
Mechanical team can complete remedial work
GMS has an in-house mechanical and plumbing division that can complete work arising from water hygiene inspections and risk assessments. This allows the company to identify compliance issues and carry out the associated remedial work through the same service provider.
The business is also registered with Gas Safe, adding domestic gas and heating capability to its mechanical services. Complii said this technical capacity was an important part of the acquisition.
Sarah Dixon, chief executive of Complii, said GMS had developed a strong reputation for water hygiene and Legionella compliance. She added that its mechanical capabilities and regional presence would strengthen the group’s Water division.
“Water safety is fundamental to protecting the people who live, work, learn and are cared for in the buildings our customers manage,” Dixon said. She added that the acquisition would allow Complii to support more customers with specialist compliance services and practical remedial work.
GMS customers gain access to wider compliance services
Complii operates five divisions covering water, air, fire, electrical systems, and lifts and escalators. GMS customers will be able to access these additional building safety and compliance services through the wider group.
Gemma Ollerton, managing director of GMS Services, said the company would retain the water compliance and mechanical expertise on which its customers rely. She said joining Complii would provide additional resources and support for further growth.
GMS works with housing associations, local authorities, healthcare organisations and education providers. Its presence in Wigan and the Midlands gives Complii additional operational coverage across central and northern England.
Complii continues water compliance acquisitions
The GMS transaction forms part of Complii’s acquisition-led growth strategy. The group has been building a portfolio of specialist businesses across several areas of building safety and regulatory compliance.
In July 2026, Complii acquired Hampshire-based Sweetbriar Limited, another provider of water hygiene, treatment and Legionella control services. H2O Global News reported that the Sweetbriar acquisition expanded Complii’s water compliance operations across England and Wales.
The addition of GMS provides further regional coverage and mechanical delivery capability. Complii has not disclosed the purchase price or other financial terms of the acquisition.
Frequently asked questions
Who has Complii acquired?
Complii has acquired GMS Services Limited, a provider of water hygiene, water treatment and mechanical services. The company is headquartered in Wigan and also has an operational base in the Midlands.
What water compliance services does GMS provide?
GMS provides Legionella risk assessments, water monitoring and testing, TMV maintenance, tank inspection and cleaning, disinfection and chlorination. It also offers water treatment, consultancy and compliance-management services.
Can GMS complete water-system remedial work?
Yes. GMS has an in-house mechanical and plumbing division that can complete remedial work identified through assessments, inspections and monitoring.
Which sectors does GMS serve?
GMS works with housing associations, local authorities, healthcare organisations and education providers. Its customers include national and multi-site organisations.
Has the value of the acquisition been disclosed?
No. Complii has not disclosed the purchase price or other financial terms associated with its acquisition of GMS Services.
