Flow, metering and water loss

What is MCERTS, and does my site need it?

• It certifies the whole arrangement. Equipment, installation, procedures and competence, not just the meter.
• Effluent flow uncertainty: better than plus or minus 8 percent of the daily volume.
• The trigger is your permit. Commonly discharges above 50 m3 per day, or where the permit states MCERTS explicitly.
• Site conformity is inspected. A certified meter installed badly does not deliver a compliant arrangement.

What MCERTS actually covers

The most common misreading of MCERTS is that it is a product label, something you satisfy by buying a meter with the right certificate. It is broader than that.

The scheme covers monitoring equipment, the competence of the people carrying out monitoring, and the organisations doing it, and it is built on established international and European standards so that regulatory data is comparable and defensible. For flow specifically, that means the certified product is only one component. How it is installed, whether the approach pipe or channel gives it the conditions it needs, and whether maintenance and calibration are documented all form part of whether the arrangement conforms.

This is why a site conformity inspection exists as a separate step from product certification. A properly certified meter installed too close to a bend, or in a channel with unsuitable approach conditions, will produce readings that do not meet the required uncertainty.

Does it apply to your site?

The obligation comes from the environmental permit, not from the scheme itself. Sites regulated under the Environmental Permitting Regulations that carry a flow monitoring requirement in their permit are expected to comply with MCERTS in order to satisfy it.

In practice the common triggers are a discharge to water above 50 cubic metres per day, or a permit or consent that names MCERTS compliance directly. If either is true the correct first action is to read the permit conditions rather than to work from a general rule, because the specific wording determines what has to be measured, to what uncertainty, and how often it is reported.

For effluent flow the headline standard is that the discharge must be measured with an uncertainty better than plus or minus 8 percent of the daily volume. That figure is what drives the installation requirements, because it is achievable with good approach conditions and not achievable with poor ones.

Where continuous monitoring fits alongside it

MCERTS governs the regulatory measurement. It does not stop a site instrumenting more broadly, and there is usually a good operational case for doing so.

The permitted discharge point is one number. Understanding what is arriving at it, from which part of the site, and how that changes through the day, is a different question and one the compliance meter alone will not answer. Where a permit limit is being approached, knowing which process contributed the volume is what allows anything to be done about it before the limit is breached rather than after.

Clamp-on ultrasonic metering is often the practical route for that supplementary picture, because it attaches to the outside of existing pipework and needs no cutting or shutdown. It sits alongside the certified compliance arrangement rather than substituting for it.