Isolating a private ring main without shutting the site down

Why a ring main, and why isolation matters

A ring main feeds buildings from both directions. If one section is shut off, water can still reach every building the long way round, as long as there are isolation valves either side of that section.
Too few valves, and a single repair can mean shutting off half the site. On a data centre, that can mean cooling water or fire water supply going down with it.

Where should the isolation valves go?

As a starting point:

• On the ring either side of every branch to a critical building, so each one can be fed from either direction.
• On each branch itself, so a building can be isolated without touching the ring.
• Either side of anything that will need regular maintenance, such as meters, strainers or pressure reducing valves.

Which valve to use?

On most private mains, a resilient-seated gate valve is the standard choice. It gives a full, clear bore when open, so it adds almost no resistance to flow, and the rubber-coated wedge seals tightly when shut.
Our Fig B03 resilient-seated gate valve is ductile iron with a blue fusion bonded epoxy coating to BS EN 14901 and a stainless steel stem. It is available from DN50 upwards to DN1200, rated PN16 with PN25 on request, and suitable for water from 0°C to 80°C.

Which options matter on an industrial site?

• Locking devices: stop valves being operated by the wrong person, which matters on shared or busy sites.
• Extension spindles: let buried valves be operated from ground level.
• Chain wheels: for valves mounted high in plant rooms.
• Clockwise or anti-clockwise close: match the site’s existing valves. More in Does the closing direction of a valve matter?
• ISO actuator flange: if the valve may be motorised or remotely controlled later.

On larger valves, a bypass can help open the main valve smoothly when there is a pressure difference across it. See Why would a large gate valve need a bypass?

Quick tip: before an emergency, walk the site with a drawing and check that every isolation valve can be found, reached and turned. A valve nobody can find is no help when a main bursts.

Before you enquire, have ready: pipe sizes, pressure rating, how the valves will be operated, closing direction, and whether any are buried or high up.

Related reading: Does the closing direction of a valve matter? · Why would a large gate valve need a bypass? · Butterfly or gate valve?