The UK plumber day rate is £350 excluding VAT on Checkatrade's figures, with MyBuilder putting the average at £368 on an unstated basis. In South London the working estimate is £400 to £450, which is the UK number carrying the London premium rather than a rate anyone has measured.
Why the London figure is an estimate
The same limitation applies to day rates as to hourly ones: no authoritative source publishes a London-specific plumber day rate. Housekeep documents London running around 20% above the rest of the UK, and Checkatrade confirms London labour on a toilet fit costs £50 to £200 more than the North. Applying that premium to £350 is the honest way to get a London figure, and it is worth saying that it is a derivation rather than a measurement.
A day costs less per hour than an hour does
This is the useful part of the published figures, and it falls out of the arithmetic rather than anyone asserting it.
Checkatrade publishes £50 an hour and £350 a day on the same guide. Divide the day by eight and you get £43.75 an hour, about 13% under the hourly rate. Two figures on one page, quietly disagreeing, and the disagreement is the insight.
The reason is dead time. A plumber booked for an hour still travels across South London, finds somewhere to leave the van and pays for it, carries the stock in and out, and does the paperwork. Booked for a day, all of that is spread across eight hours instead of one. Longer bookings are cheaper per hour because the overhead is shared out.
When a day rate is the right basis
Day rates suit work with a known shape and an unknown duration. Repiping a bathroom, moving a run of pipework for a kitchen refit, or working through a list of small jobs in one visit are all day-rate work. So is anything where a plumber cannot see the whole problem until the boxing comes off.
Bundling matters here. If someone is already in the house for a morning, adding a stiff stopcock, a slow-filling cistern and a dripping tap to the visit costs a fraction of three separate call-outs. The travel and the call-out charge are paid once.
When hourly or a fixed price is better
For a single defined job, such as one tap replaced, one blockage cleared or one radiator valve swapped, a fixed price is usually the cleanest basis, because the plumber carries the risk of it taking longer than expected. Checkatrade prices plenty of small jobs that way: unblocking a sink or toilet at £60 to £90 excluding VAT, replacing a tap at £140 average labour, replacing a stopcock at £140 to £240. The tap and stopcock guides do not state whether their figures carry VAT, so ask which basis a quote built on them uses.
Larger installation projects move off day rates entirely and get quoted as a complete job rather than as days on site. Where that happens, the number to ask for is a single written price for the whole works, with the labour and materials separated out, so the quote can be compared against another on the same basis.
What the day rate does not include
A day rate is labour. Parts sit on top, and Housekeep notes that plumbers commonly add 20 to 25% on materials. That is a single source without published methodology, so it is worth asking about rather than assuming. Nothing dated establishes it as a standard.
VAT is the other line. Checkatrade's figures exclude it and homeowner quotes normally include it, so £350 excluding VAT is £420 to a domestic customer paying it. Comparing a VAT-exclusive rate against a VAT-inclusive quote makes the honest quote look expensive.
Reading a day-rate quote
Ask what a day means: seven hours, eight, or on site until the job is done. Ask whether a second person is included and whether that person is a qualified plumber or an apprentice. Ask what happens on the second day if the first runs over, and whether the call-out charge applies again.
Ask which basis your quote is built on before the van arrives, not after.