How Google picks the three
Google says it ranks local results on three things: relevance (does your profile match what was searched), distance (how far you are from the searcher) and prominence (how well known and well reviewed you are). You can’t move your van closer to every customer, so the work is on the other two.
1. The wrong category, or too few services
Your primary category should be "Plumber". I still find profiles set to something vaguer, or with the services list left empty. Every service you add (boiler repair, leak detection, bathroom installation) is another way for your profile to match a search.
2. A service area that covers everywhere
A big radius feels like it should bring more work. In practice it makes the profile less relevant to each town inside it. List the towns you take jobs in, and back that up with photos and posts from jobs in those towns.
3. Hours that say you’re closed
If you take emergency calls in the evening but your profile says you close at 5pm, Google will often show someone else. Set your hours to when you answer the phone, and mark emergency service if you offer it. Then make sure you do answer.
4. Reviews that stopped
Plenty of plumbers have a good rating built up years ago and nothing since. Recent reviews matter, both to Google and to the person deciding who to ring. The fix is a habit: send a direct review link by text when you finish a job, while the customer is pleased.
Reply to every review, good or bad. A calm, helpful reply to a complaint does more for the next customer than another five stars.
5. Different details on different sites
Old phone numbers on Yell, a former address on Checkatrade, a slightly different business name on a supplier’s installer list. Each mismatch makes Google a little less sure about your business. Pick one version of your name, address and phone number and make every listing match it.
6. A website that doesn’t back the profile up
Google checks your website to confirm what you do and where. One page that says "all plumbing work undertaken" doesn’t help. A page for each main service, a clear list of areas you cover, and a phone number that’s easy to tap on a mobile all do.
Where to start
Fix the category, services, hours and service area first. They cost nothing and take an afternoon. Then build the review habit, tidy your listings and look at the site. I go through all of this in more detail in the local SEO guide for plumbers, including what I’d do in your first 90 days.
If you’d rather I looked at your profile for you, the free audit covers every point above.