Internal drains are the waste pipes inside your home. They run from sinks, baths, showers, toilets and appliances to the drain outside. Hair, soap, fat, paper and wipes are the usual causes of a blockage, because they stick to pipe walls.
The pipes run behind walls and under floors, so the blockage is hard to see. The slow fixtures tell you a lot. One slow sink points to its own trap, while several slow fixtures point to a shared pipe.
An engineer can use hand rods, a powered snake or a small jetter. The choice depends on the pipe size and the type of blockage. Washing machines and dishwashers share the same pipes, so a machine that will not drain may point to a blocked waste pipe or trap.
The engineer checks which fixtures are slow. That shows whether one trap or a shared pipe has the blockage, because a shared pipe affects every fixture on it.
Rods, a powered snake or a small jetter clear the pipe. The engineer may take off a trap under a fixture and clean it, while the rest of the run is cleared with a tool.
Water runs from the connected fixtures to check for a second blockage further along. Ask the engineer to test every fixture on the run, since a second plug is easy to miss.
The engineer refits the trap or access panel and wipes down surfaces. Check that each fixture drains freely before the engineer leaves, because it is easier to fix then.
Prices vary because the type of blockage differs. A single clogged trap is usually a smaller job than a shared pipe run or a blockage that needs a camera.
Ask for a written quote before work starts, since a shared pipe can mean more work. Ask whether there is a call-out charge, and ask what the price covers if the blockage is in the shared pipe.
When more than one fixture is slow, the blockage is probably in a shared waste pipe or in the drain outside. This is common where fixtures connect to one pipe before it leaves the building, because they all share the exit. Describe which fixtures are slow when you send your request.
It can, because a blocked drain may leak at a pipe joint, overflow from a trap or back up through a fixture. Dealing with it quickly lowers the risk of damage to plaster and floors.
Often not, because many traps and rodding points can be reached without lifting anything. Ask the engineer how they plan to reach the pipe. If access is a problem, ask about the options before work starts.