Isolation Valves And Why A Building Needs Them

Every plumbing emergency has two parts: the failure, and how much of the building has to be shut down to fix it.

The second part is decided years earlier, by where the isolation valves are and whether they work.

What a valve is for

An isolation valve lets you shut water to one part of a system without shutting the rest.

A valve under a basin isolates that tap. A valve at the entry to an apartment isolates that apartment. A valve on a riser isolates a column of apartments. Without them, the only option is the main.

Shutting the main on a residential building means notifying everyone, choosing a time, and giving people no water while the work happens. For a burst that cannot wait, nobody gets notice at all.

The three failures

No valve at all. Common in older buildings, where individual apartments were never isolated. A tap replacement in one unit becomes a building-wide shutdown.

A valve that will not turn. Far more common. The valve exists, it has not been operated in fifteen years, and the spindle has seized. Forcing it snaps the handle or splits the body, which turns a small job into a flooded cupboard.

A valve that turns but does not seal. It closes and water keeps trickling through, so the work cannot be done dry. Old gate valves are particularly prone to this, because the gate corrodes away inside the body.

Why they seize

Valves fail from not being used.

Mineral deposits build up on the spindle and the seat. Old gate valves corrode internally. Rubber washers harden. None of it happens quickly, and all of it is invisible until the day it matters.

A valve operated once a year stays free. A valve left alone for a decade is a gamble.

What to replace them with

Quarter-turn ball valves, rather than the multi-turn gate valves used in older buildings.

A ball valve either opens or closes, there is very little to seize, and you can tell at a glance whether it is open by the handle position. Gate valves give no visual indication at all, which is its own problem during an emergency.

What a building should actually have

An isolation point at the entry to every apartment, accessible without entering another unit.

Isolation on each riser, so a fault in one column does not affect the others.

Isolation to plant, hot water systems and common area fixtures.

Valves that are labelled. An unlabelled valve in a service cupboard full of unlabelled valves is worth very little at 2am.

And a plan, on paper, showing what each valve controls. Every building should have one, and very few do.

The maintenance that prevents the emergency

Operate every valve once a year, fully closed and fully open, and record it.

Replace anything that binds, weeps or will not seal, while it is a planned job rather than an emergency one.

Label as you go.

This is unglamorous work and it is one of the highest-value things a building can do, because it changes the scope of every future plumbing job. The same thinking applies to [water meters and leak detection](/blog/water-meters-sub-metering-and-leak-detection): knowing where the water is and how to stop it is most of the battle.

What it looks like when it is missing

A flexible hose bursts in a bathroom. There is no working isolation for the apartment.

Water runs while someone finds the building main, which is in a locked cupboard. By the time it stops, it has reached two apartments below, and now there is a [ceiling water damage](/blog/water-coming-through-a-ceiling-in-an-apartment) job as well as a hose replacement.

The hose was always going to fail. The valve was the part that could have been ready.