When drainage has slowed

What a professional will be trying to work out

These are the distinctions a professional makes when they attend. They are questions, not conclusions — and knowing them lets you follow the conversation rather than just receive its result.

• whether the change was gradual or sudden
• how many fixtures show it
• whether it varies with the amount of water used
• whether it has ever fully blocked

What is worth writing down

These details are cheap to record now and impossible to reconstruct later.

• approximately when it began
• whether it was gradual or sudden
• which fixtures are involved

Evidence that would change the next decision

If you are deciding whether something is worth paying for, these are the things that actually move the decision.

• roughly when the change began
• whether it affects fixtures on more than one level
• whether it improves after a clearing and for how long

Where gradual and sudden lead

Cleaning the line is usually the first thing discussed, and it is worth being clear about what a clearing does and does not establish before agreeing to it. Flow improving is a fact about flow; it is not a description of the pipe.

A change that arrived gradually and one that arrived overnight send a professional down different paths, and neither on its own establishes that the pipe is damaged. What separates them is somebody putting a camera down the line and writing down where the picture changes.