REFURBISHMENT | DRAINAGE STACKS WHEN DRAINAGE REPLACEMENT STACKS UP Overcoming the challenge of drainage stack replacement means coming up with new solutions, which can include prefabrication, says Polypipes Graham Hicks D rainage stack replacement in repair, maintenance and improvement projects can present complex challenges, particularly in public sector housing work, where a whole host of factors must be considered if the project is to be completed efficiently. Drainage stack replacement is a major piece of remedial work, which for public sector housing projects inevitably means some period of time during installation when residents are without the use of their sinks, toilets and other facilities. In multiple occupancy buildings, where there are perhaps 100 or more individual homes, this can mean a significant level of disruption. Replacing old drainage with prefabricated stacks can save time on site compared with the traditional approach of replacing individual components that need to be welded. The use of standard loose parts will not always be suitable for an older building after it has undergone previous phases of renovation. The older it is, the more likely it is that whats on site will differ from original plans. Bathrooms may have been moved or reconfigured, and additional appliances may have needed extra drainage. The proximity or angle of joints needed may not match standard parts, so may demand further work to address. This means more time on site and, potentially, will affect the layout of some rooms. Potential solutions Looking at how drainage stacks are manufactured and designed to the requirements of individual projects can make a big difference to how these problems are overcome. Recent work carried out by Polypipe Building Service at a large, ageing tower Drainage stack replacement is a major piece of work that can cause significant disruption block in East London is a good example of this. The existing metal drainage system had reached the end of its useful life. On inspection, some of the horizontal pipework connecting the individual perimeter stacks to the main stacks on the third floor had corroded. However, because of the layout of the building, and the alterations of more than five decades of renovations, a series of adaptation works were needed. These included designing soil stacks with very compact waste connections set at angles, often tightly spaced above each other, while avoiding any potential for cross-flow issues. Custom engineering solutions were needed because of different layouts in some of the flats for example, one had a different bathroom configuration from all the other flats within the building, with Standard loose parts will not always be suitable for an older building after previous phases of renovation additional waste connections. A separate set of drawings was created for the installer, detailing all the parts of the stack and part numbers for that specific area. Because of the complexity of the project, several test stacks were created to overcome initial installation issues that were experienced. This allowed the right size and configuration of stacks to be prefabricated off site, and minimised the amount of time required during installation to overcome problems that might otherwise have added days or more to the schedule. All of the stacks provided were pre-air pressure tested to offer complete peace of mind to the contractor, and are designed and manufactured to the existing BS EN 12056 (Parts 2 and 3) and Building Regulations Part H standards and regulations. An efficient solution The problems outlined are not uncommon for work of this type, with the need to consider minimising disruption to occupants and addressing decades of changes and renovations potentially adding significant time to a project. This can be largely avoided, however, by using an offsite, prefabricated approach for drainage stacks. CJ GRAHAM HICKS is project development manager at Polypipe Building Services www.cibsejournal.com October 2022 79 CIBSE Oct 22 pp79 Pipework RMI.indd 79 26/09/2022 17:41