How to Fit a Kitchen Tap: Mixer and Monobloc Installation

Out with the Old, In with the New

Kitchen tap replacement is one of the most common plumbing jobs. Modern monobloc mixers are easier to fit than old pillar taps, but there are still tricks to know. Here's the full process.

Before You Start

Check compatibility:

• Count holes in your sink - usually 1, 2, or 3
• Measure hole diameter (usually 28mm, 32mm, or 35mm)
• Check flexible tail length needed to reach valves
• Confirm hot is on left (standard in UK)

Turn off water:

• Close isolation valves under sink if fitted
• Or turn off at mains/stopcocks
• Open tap to drain pressure

Tools and Materials

• Basin wrench (tap spanner) - essential for awkward access
• Adjustable spanners
• Drill if fitting isolation valves
• Plumber's silicone grease
• PTFE tape
• Bucket and towels
• Torch - it's dark under there

Removing the Old Tap

1. Disconnect supply pipes
   • Put bucket underneath
   • Undo compression fittings or push-fit connectors
   • Let water drain
2. Undo tap fixing
   • Usually a large nut underneath sink
   • May be brass backnut or threaded rod with nut
   • Basin wrench essential for access
3. Lift out tap
   • May need to work free if sealed with silicone
   • Clean sink top around holes

Fitting the New Tap

Monobloc mixer (single hole):

1. Fit flexible tails to tap (use washers, hand-tight plus quarter turn)
2. Fit rubber seal/gasket on tap base
3. Insert tap through sink hole from above
4. Fit horseshoe washer and backnut from below
5. Tighten backnut while holding tap straight
6. Connect flexible tails to supplies

Tips for the awkward bit:

• Pre-fit everything you can before going under the sink
• Basin wrench lets you reach in tight spaces
• Headtorch keeps hands free
• Don't overtighten plastic nuts - they crack

Connecting the Supplies

With isolation valves (best option):

• Flexible tails usually connect directly
• Check thread size matches (usually 15mm or 1/2")
• Use fibre washers - don't need PTFE tape with compression
• Hand tight plus quarter turn with spanners

Without isolation valves:

• Connect to service valves or copper pipe
• May need adaptors depending on setup
• Consider adding isolation valves - makes future work easier

Testing

1. Open isolation valves slowly
2. Check all connections for leaks
3. Run tap and check operation
4. Hot on left, cold on right
5. Check spray head if fitted
6. Leave bucket in place for 24 hours - slow leaks appear overnight

Common Problems

Tap won't fit through hole:

• Hole may need enlarging (careful with stainless)
• Or wrong tap for your sink

Can't tighten backnut:

• Get proper basin wrench
• Or use tap mounting kit with studs

Tails don't reach valves:

• Buy longer flexible tails
• Don't stretch or kink them

Leak at flexible tail connection:

• Check washer is in place
• Don't overtighten - damages seal
• Replace washer if reusing old one

Pull-Out Spray Taps

Additional considerations:

• Weight or counterbalance system needs space below
• Check spray hose routing before tightening
• Test retraction mechanism before finishing

The Bottom Line

Kitchen tap fitting is 90% preparation and access, 10% actual plumbing. Get proper tools - especially a basin wrench - and take your time. Check everything is dry before packing up. A well-fitted tap should last years without issues.

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