Short answer
Reply calmly, in public, within a day or two. State the facts without arguing, offer to sort it offline, and keep it short. The reply is not aimed at the reviewer, it is aimed at the next customer reading it, who is deciding what you are like to deal with.
Every plumber gets one eventually. Usually it is either a job where something genuinely went wrong, or a customer who misunderstood the quote. Occasionally it is somebody having a bad week.
The instinct is to explain yourself at length. Resist it.
Who the reply is actually for
Not the person who left the review. They have made their mind up and you are unlikely to change it.
The reply is for the next customer, who is scrolling your profile deciding whether to ring you. They will read the bad review, then read your reply, and form a view about what you are like to deal with when something goes wrong.
That is the entire job of the reply. Once you see it that way the right tone becomes obvious.
What to write
Four things, briefly:
- Acknowledge it. Not a grovel, just recognition that they were not happy.
- State the facts plainly. If the quote covered one thing and they expected another, say so in one sentence, without sarcasm.
- Offer to sort it offline. A name and a number. This signals to everybody reading that you are willing to fix things.
- Stop. Three or four sentences is plenty.
Something like: sorry this was not what you expected, Dave. Our quote covered the cylinder replacement but not the pipework we found behind the wall, which we rang you about before starting. Happy to go through it, give me a ring on the office number.
That reads as a real business having a normal disagreement. It does you no harm at all.
What never to write
Do not argue point by point. A long rebuttal makes you look like hard work, even when every word is true.
Do not accuse them of lying, even when they are. The next reader has no way to judge who is right, and the person who stayed calm wins by default.
Do not mention anything private. Their address, their payment history, what their bathroom looked like. It is a public page and it reflects on you.
Do not leave it three weeks. A reply a day or two later looks attentive. A reply a month later looks like you only noticed because somebody mentioned it.
When it is genuinely not your customer
It happens, usually a mix up with a similarly named business. Report it to Google, and reply publicly saying you have no record of the job and inviting them to contact you so you can check.
Be prepared for the report to go nowhere. Google removes fewer reviews than people expect.
The real protection
A steady flow of recent reviews.
One fair criticism among plenty of recent positives reads as a normal business having a normal off day. The identical review sitting on top of nothing since 2023 is what actually costs you work, because it becomes the only recent information anybody has about you.
This is why an automatic review system matters more than any individual reply. It is not about burying criticism, it is about the bad one being one voice among many rather than the only voice in the room.