Bonding on sink?

by Steve on May 4, 2009



Do I need to carry out supplementary bonding on a sink?


Probably not.

On-Site Guide section 4 states that:

Supplementary bonding is required by BS7671 701.415.2 in some locations.

(Generally in Special Locations. A kitchen or utility room is not one of these).


However, if the installation meets the requirements for earthing and bonding (ie. Main earth connection and Main bonding of gas and water, metal waste pipes etc. 411.3.1.2 ) then there is no specific requirement for supplementary bonding of:

  • Kitchen sinks, pipes or draining boards

  • Metallic boiler pipework

  • Metal furniture in kitchens

  • Locations containing bath or shower providing the requirements of BS7671:2008 701.415.2 are met. (Disconnection time of 0.2 for, TT 0.4 for TN and RCD protection).


Note: Metal waste pipes must be bonded to the main earthing terminal as they are extraneous conductive parts.


Source information:

On-Site Guide section 4

BS7671:2008 411.3.1.2

BS7671 701.415.2

{ 2 comments… read them below or add one }

James August 17, 2011 at 06:24

It is worth mentioning that 701.415.2 states that three criteria must be met before supplementary bonding may be omitted in a location containing a bath or shower and not just the two you have mentioned. It is also essential to verify the exposed metal is effectively connected to earth.

This can only be done by measurement and a value of that less than that specified by regulation 415.2.2 means it can be omitted. Higher than that value and you have to fit it desipt achieving correct disconnection times and having all circuits protected by RCDs. April 18, 2011 at 14:27

Phew that saved me some extra work all sorted now

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