Outdoor tap leaking? Three fixes before you call a plumber

Outdoor taps are a bit out of sight, out of mind. You notice the drip in May, you think "I'll fix that in June," and by July it's become a permanent feature. Here's the right way to sort it, starting with the cheapest fix.

Isolate the water first

Outdoor taps usually have an isolator valve on the pipe inside the house. Look on the wall near where the tap goes through, or under the kitchen sink if that's the nearest point. Small valve, screwdriver slot on top, turn 90 degrees to isolate.

If there's no isolator, you'll have to use the main stop tap, which is usually under the kitchen sink or in the cellar or utility room. Always isolate before unscrewing anything.

Diagnose the leak

Same rules as the kitchen tap post. Watch for a minute. Where is it actually leaking from?

• From the spout after it's turned off: worn washer.
• From around the handle: spindle gland or O-ring.
• From the base where the tap meets the wall: compression fitting behind the wall, or wall itself.
• Water on the wall below the tap, wet patch on interior wall on the other side: split pipe inside, probably from a frost last winter. Not DIY.

Fix 1: Replace the washer (90% of leaks)

A dripping outdoor tap is almost always a perished rubber washer. Half an hour's work, £1 in parts.

1. Isolate water. Open the tap to drain it.
2. Undo the large hex nut at the body of the tap (below the handle) with a big adjustable spanner or a 22mm spanner.
3. Pull out the spindle assembly. At the bottom end you'll see a rubber washer held by a small screw or just pressed into a cup.
4. Replace with a new one. Tap washers come in standard sizes. A pack of assorted sizes is £3 from Screwfix.
5. Smear the threads with PTFE tape or silicone grease on reassembly.
6. Turn the water back on slowly and check.

Fix 2: Spindle gland or O-ring

If it's leaking from around the handle when the tap is on, it's the gland. There's a small nut at the top of the body (sometimes called the packing nut). A quarter-turn tighter with a spanner often stops the weep. If it's still leaking after that, take the spindle out, replace the top O-ring (£1) and refit.

Fix 3: Compression fitting at the wall

If water is appearing at the base of the tap on the wall side, the compression fitting behind the brick has loosened. Usually just needs a quarter-turn tighter. The fitting is directly behind the tap in the hole through the wall. You'll need a stubby spanner or a set of gripping pliers.

If the fitting itself is corroded (greenish-white crust) rather than just loose, it wants replacing. A bit more involved, and sometimes needs the wall plate removed. 90 minutes.

The frost damage case

If water is appearing anywhere it shouldn't, particularly on the inside wall of the house behind where the outdoor tap is fitted, you might be looking at a split pipe from last winter. Classic symptoms:

• Water only shows when the tap is on
• Wet patch appears on interior wall
• Pressure drops at the outdoor tap even when everything's open
• You forgot to isolate the outdoor tap in November

This isn't a handyman job. It's a plumber job, because it usually involves cutting into the wall, accessing the split section, and jointing in a new piece. I can usually point to the leak, confirm the symptom, and recommend a local plumber. I don't do hidden pipe work myself, and I'd rather tell you that than have a go and cost you more to fix twice.

Before next winter

The number one outdoor tap conversation I have every spring is about frost damage. It's preventable. Two things:

• Isolate the outdoor tap in October. Close the interior isolator. Open the outdoor tap to drain the standing water. Leave it open over winter.
• Fit a tap cover (£4, like a little woolly sock for the tap) over the spout. Stops freezing on really cold nights.

Two minutes of autumn work saves you a £200 pipe repair in March.