In the last post, I wrote about the pros and cons of metering individual premises. That article went on to briefly mention the possibly needing a compound meter, if a master meter were to be installed. So, what exactly is a compound meter…?

Compound meters

Compound meters (sometimes referred to as high/low meters because they have high and low flow sides) are used in situations where large volumes of water need to be metered, but at other times slower flows must also be recorded.

Such a scenario could be a large, multi-unit apartment building or a hotel that must be able to meter high usage first thing in the morning, when many residents are showering at the same time, but also measure low flows in the middle of night to record the occasional toilet flush. A manufacturing plant that uses large volumes of water while the plant is in operation, and minimal usage at other times, is another example of a prime candidate for a compound meter.

The Alliance for Water Efficiency has a good, easy to understand description of compound meters in this article.

For billing purposes, with compound meters, two sets of meter readings are taken – a larger meter for the high flows (the “high side”) and another, smaller meter, for the low flows (the “low side”). The usages are then added together and the customer is billed for the combined usage.

Don’t be fooled

The “high side” of a compound meter may not always be the higher reading of the two. The high side could have already rolled over, and have a lower reading, or there could be relatively little high demand. In the latter case, most of the water used would be metered by the “low side”.

Does your billing system support compound meters?

Many older billing systems don’t properly support compound meters. Some require creating two accounts – one for the high side meter and another for the low side meter. Others require manipulating the readings before entering them as a single, combined meter.