Office Block Seals 300 Corroded Pipe Joints in 250-Metre Long Cast Iron Rainwater Stack Repair

An office block refurbishment in London is kept on track as 300 corroded joints in an internal rainwater stack are sealed as part of a repair which prevented the time-consuming replacement of the entire 250-metre-long cast iron pipe system running through the five-storey building.

Case Study Overview

Site Office block
Location London, UK
Pipe Type Cast iron rainwater stack
Repair Type Leak repair
Products Sylmasta AB Original Epoxy Putty

Pipe Defect

With the entire office block stripped out as part of the refurbishment, the internal cast iron rainwater stack running for 250 metres through the five storey building was accessible for the first time in decades.

An inspection of the stack revealed many of the 30-year-old rubber seals joining sections of pipe together had failed and needed replacing. When these seals were removed, the pipe ends underneath were discovered to be badly corroded where water had become trapped.

As a result, the pipe ends were uneven, pitted and breached in places. The damage meant achieving a watertight seal between sections of pipe when rejoined together was now impossible.

The engineering company carrying out the refurbishment tried new rubber seals, metal seals, pipe repair clamps and repair clamps with teeth but to no avail.

When the joints continued leaking, it appeared the only option would be to replace the entire 250 metres of pipework at considerable cost and delay to the refurbishment.

Corrosion had left the pipe ends pitted, uneven and breached. It was impossible to create a watertight joint using seals or clamps

SylWrap Solution

Sylmasta were asked to visit the office block to see if a repair method for the rainwater stack could be formulated. It was decided to use Sylmasta AB Original Epoxy Putty to seal each of the new repair clamps against the pipe.

Enough putty was cut from a 200g AB Original Stick and kneaded by hand. Whilst soft, the putty was forced into both ends of the clamp. It filled all gaps between the clamp and the uneven pipe surface, curing to form a rock-hard, waterproof material which permanently sealed any leak paths.

The two-hour work time of AB Original allowed the team making the repairs to thoroughly seal every joint at a reasonable pace without fear the putty would harden before being fully pushed into the gaps.

Having seen how straightforward and effective the repair was on the new clamps, the team then decided to apply AB Original to all 300 joints across the entire rainwater stack.

AB Original was packed in and around the original rubber seals, giving the team full confidence the system would not start leaking through joints once it was boxed back in and inaccessible at the end of the refurbishment.


120kg of AB Original was used for the repair, which took two days to complete. Supplying the epoxy putty in stick rather than two-part format eliminated the need to measure out separate components of Part A and Part B, making application quicker.

Follow Up

The refurbishment of the office block was completed almost to planned schedule with the only minor delays caused by problems unrelated to the rainwater stack.

Had replacement been required instead, a whole new rainwater stack would have needed to be fabricated and installed through all five floors, taking weeks and holding up the refurbishment significantly.

Products Used

AB Original Epoxy Putty
Epoxy putty with a two-hour work time for thorough sealing of leaking pipes and joints

Related Case Studies

If you have an application you would like to enquire about, then please get in touch

Call: +44 (0)1444 831 459