SANS 10254 and under-counter water heaters

By Patrick Gordon

The problem facing many installers is how to get hot water to isolated terminal points. This is especially so where you need to eliminate long dead legs.

The current solution is to use a small under-basin/sink geyser. The problem that faces the installer is how to install the unit in compliance with SANS 10254. Why would this be a problem?

SANS 10254 requires that all pressurised hot water vessels be installed with five basic ancillaries: 1) T&P safety valve; 2) Pressure reducing valve; 3) Expansion relief valve; and 4) Two vacuum breakers. Anybody that has ever installed one of these units will know that it is virtually impossible to do so.

It is however possible to install it according to SANS 10254 as an open-vent system. This means that at all times the internal pressure in the heater will be open to vent to the atmosphere. This can only be achieved by using a specially designed mixer or connection convention.

The correct connection takes cold water and pushes it into the heater. This causes the pressure in the heater to rise (we know that this is not allowed); the outlet of the heater is then connected to an unrestricted outlet that releases the heater’s internal pressure. This having happened, the internal pressure is kept reduced to atmospheric and we are thus still compliant with SANS 10254.

Figure 1Figure 1: Installation drawing for open-vent geysers in SANS 10254.

NOTE 1   The combination of a hot water control valve and swivel-type outlet may be replaced with a mixing control valve unit of a type shown in Figures 1 and 2.

NOTE 2   The drip tray is not required for over-basin (such as a sink or bath) installations.

NOTE 3   The cold water supply connection between the control valve and the water heater should be furnished with a spring-loaded non-return valve.

Figure 2

Figure 2: Typical open-vent mixing control valve unit for under-sink water heaters.

As can be seen from Figure 2, this mixer can be identified by the fact that it has three connection hoses instead of the normal two.

An advantage of this configuration is that the installer does not have to worry about trying to balance the water pressure at this installation. It also makes the installation cheaper than a regular hot water cylinder installation as you only need one cold water supply pipe.

Remember, all SANS 10254 installations must be issued with a CoC. SANS 10254 says the following: On completion of the installation, a certificate of compliance from the professional body for plumbers registered in terms of the relevant national legislation (see foreword), shall be issued to the owner of the installation or to the body requiring such a certificate.

I hope this article will help you to understand how to make your installations safer and legal.

Advertise on Plumbing Online
August 2019

PA PlumbdrainLogo100 PlumbingOnline150 TP

Product of

IMD logo White

Interact Media Defined (IMD), is one of South Africa’s leading multi-media magazine publishers READ MORE

Talk to us

JHB T : +27 (0) 11 579 4940
CPT T : 0861 727 663
E :

13A Riley Road, Bedfordview,
South Africa 2007


Cookie policy
Privacy & Cookie policy
Privacy policy

© Interact Media Defined