Why is my water meter is running backwards?

An example of a MuniciPal water meter

A borehole, used to water the garden, is also supplying water to the house BUT the municipal water meter is running backwards. No prizes for guessing what’s happening here! The pressure delivered by the borehole pump is higher than the mains supply. This means the borehole water is running back into the municipal supply. This is NOT an acceptable situation and MUST be sorted out ASAP. This is not only illegal, but could be detrimental to the health of everyone in the immediate area. Under no circumstances must borehole water be forced back into the mains system.

What to do to solve the problem

Option 1: Have a Backflow Preventer Valve fitted

Figure 1: Type BA & type BM backflow preventer valves
(Courtesy of SOCLA valves)

This will require the services of a registered plumber who has had experience with the selection of these types of valves (yes there are different types for different levels of sanitary protection). Essentially, there are two non-return valves (n.r.v.) separated by an isolation chamber. During the closing cycle, residual borehole water will be retained in this chamber and exhausted to atmosphere. They are available from valve companies and larger hardware retailers.

Option 2: storage tank with separate piping systems

Have an plastic storage tank installed which has borehole and mains water supplied through two separate piping systems. The borehole pump should be controlled with a liquid level relay while the mains supply can be controlled with a float valve.
Both supply lines to the tank must be fitted with good quality nrvs. A booster pumpset supplies the house with presssurised water drawn from the tank.

Figure 2: Using a storage tank and booster pump set

Figure 3: Alternative solution

 
Option 3: An alternative solution

A three-way ball valve is fitted after the discharge elbow at the top of the borehole.

The diagram shows the connections to be made. Depending on the orientation of the three pipes, additional fittings (nipples, tees and/or elbows) will be required.

Submitted by John Tonkin

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FYI: Water Quality testing

If you are making use of borehole water in the home, make sure that the water is tested at least every 12 months. However, you should be guided by the SANAS accredited laboratory that carries out the analysis, as they will be able to offer advice that is specific to your context. It’s for your wellbeing and those around you. The following article published in the Borehole Water Journal Online gives more information about groundwater that is to be used for drinking purposes. Is all groundwater safe enough to drink?