Build the page that tells somebody how to stop the water
The most useful thing a plumbing site can contain is instructions for the sixty seconds before anybody could possibly arrive.
Somebody with water coming out of something needs to know where the shutoff is, how to turn it, what to do if it will not move, and what to shut off if they cannot find the main. That is a page, and remarkably few plumbing companies have one.
It should be findable in a hurry, which means linked from the home page rather than buried in a blog, and written so it can be followed by somebody who is panicking and holding a phone in one hand.
Include the parts people get wrong. Where the main usually is in different kinds of houses, why an old valve sometimes will not close, how to shut off a water heater, and when to stop trying and call.
The commercial worry is that it costs you a call. In practice it does the opposite: somebody who just saved their kitchen floor because of your page is going to call you, and they are going to tell people about it.
It is also one of the few genuinely link-worthy pages a plumbing company can publish. People share it, other sites reference it, and it keeps working for years.