1. TMCO HYDRAULIC SERVICES – BACKFLOW PREVENTION HOW DID TYPICAL BACKFLOW PREVENTION DEVICES PERFORM THROUGH THE CHCH EARTHQUAKES? PRESENTED BY: MIKE BAKER

2. INTRODUCTION Speaker: Mike Baker TM Consultants Ltd - EECA FUNDED - 35 staff - All services - All projects - All locations

3. ENCLOSURES AND DEVICES -University of Canterbury installation.

4. ENCLOSURES AND DEVICES -Note seepage caused by silt or blockages

5. ENCLOSURES AND DEVICES -Sturdy enclosure -Clearance under doors to allow adequate runoff

6. BACKFLOW DEVICE OVERVIEW -No external damage to backflow preventers -Foundation pad, thrust blocks and enclosures performed well -Leaky devices caused by non-localised liquefaction and small stones -Most problematic devices simply required a cleanout -Few devices required new parts -Steel spools through slab helped with above slab stability

7. BACKFLOW DEVICE OVERVIEW -Encountered damage in cracked seats for the devices, more prevalent after earthquakes -Possible water hammer and increased pressure resulting from earthquakes damaged devices -Hairline cracks in balls causing leaks -Increase in particles and stones from mains pipework blocking devices

8. INSTALLATION - High mass valve assembly support was critical to avoiding damage.

9. PIPING -Pipe work was the main issue with damage to backflow assemblies being secondary to this.

10. OTHER ISSUES -Illegal temporary unprotected connections were prevalent. Many still remain. - Backflow did occur, witnessed by foaming in broken street mains near commercial/industrial buildings. Maybe backflow from inadequate air gaps. -Frost protection, particularly for those devices unused over winter (spring, cartridge, test cock failures). -Water hammer theory.

11. OVERALL -Installation-wise I believe we are doing well. -Rigidity and support are key. -Keeping silt, stones and other debris out of the system is important. -Frost protection, particularly for those devices unused over winter (spring, cartridge, test cock failures). -A TA check up on existing systems would be prudent to check for illegal systems.