New standards. Updated systems. Is your siphonic drainage still compliant?



With the recent revision of BS 8490, the bar has been raised for siphonic roof drainage systems. One of the most notable changes? The mandatory inclusion of secondary overflow provisions for internal gutters — a critical update reflecting the UK’s increasing rainfall intensity and the need for resilient, fail-safe drainage design.

Over the past decade, system designs have evolved significantly. What was compliant ten years ago may now fall short — and that could mean increased risk of blockages, water ingress, or costly failures.



At TGM, we offer certified inspections, cleaning, and repairs to ensure your system:

✅ Meets the latest BS 8490:2025 standards
✅ Performs at peak efficiency
✅ Reduces long-term maintenance costs

As proud members of the SRDA, we don’t just maintain your system — we future-proof it.