How do I replace a bath tap without taking the bath out?

Bath taps sit at the far end of a space designed to be filled with bath, not with a person. The plumbing is identical to a basin tap; the difficulty is entirely about reach, light and leverage.

What you'll need

• A basin wrench with a long reach
• Flexible tap connectors and isolating valves
• A torch or head torch
• Penetrating spray, cloths and a bowl
• A mini hacksaw as a last resort

Step by step

1. Get proper access first.Take the panel off. If the bath is tiled in, cut a neat access hatch in the panel or boxing and fit a proper access panel — every future job needs it too.
2. Light the space properly.A head torch and a second light. Working by feel behind a bath is how nuts get cross-threaded and pipes get kinked.
3. Turn the water off and drain down.If there are no isolating valves, close the stopcock and open the lowest taps in the house to drain the pipework. On a gravity hot system you may also need to tie up the tank ballvalve.
4. Disconnect the supplies at the tap.Undo the tap connectors. Have a bowl ready — a bath supply holds a surprising amount of water even after draining.
5. Free the backnuts.Penetrating spray, then a long-reach basin wrench. Bath tap backnuts are usually worse than basin ones because they have been wet for decades.
6. Cut the tails if the nuts will not move.A mini hacksaw or a rotary tool through the old tap tails releases the tap. It is destructive to a tap you are replacing anyway, and far quicker than fighting a corroded nut.
7. Clean the bath's tap platform.Scale, old sealant and rust stains all stop the new tap sitting flat. Clean it back properly, and check the acrylic is not cracked around the holes.
8. Check the new tap's centres.Standard UK bath tap centres are 180mm. Confirm the new tap matches the existing holes before you get committed.
9. Fit the tap with its gasket and tighten evenly.Firm rather than brutal. Acrylic baths flex, so use the supplied backing washers to spread the load rather than tightening against bare acrylic.
10. Fit isolating valves and flexible tails.One valve on each supply, then flexible tails to the tap. Buy tails long enough to curve gently rather than kink.
11. Refill and test at full flow.Turn on slowly, run both taps hard, and check every joint by hand. Then check again after an hour and after the first bath.

Tips

• Fit isolating valves even if nothing else needs them. It converts a two-hour job into a ten-minute one next time.
• Standard bath tap centres are 180mm — measure the existing holes before buying anything.
• Keep a torch pointed at the joint while you tighten. Working blind is how tails get cross-threaded.

Common mistakes

• Buying the tap before checking the hole centres — Bath taps come in single-hole, 180mm two-hole and three-hole deck sets. A mismatch means new holes in the bath, which on an acrylic bath is a real job.
• Tightening the backnut hard against acrylic — Thin acrylic crazes and cracks around the tap holes. Use the plastic backing washers supplied and tighten only enough to hold the tap steady.

If it doesn't work

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