Why the Same Drain Keeps Blocking
A drain that blocks once has caught something. A drain that blocks every few months has a defect. Repeat blockages mean the pipe itself is holding material back, through a belly, a displaced joint, root ingress or a rough internal surface that everything catches on.
What actually builds up
Cooking fat leaves the pan as a liquid and reaches the pipe as a solid. It coats the pipe wall, hair and fibre bind into it, and wet wipes arrive and bridge across whatever is already there. None of that is unusual. What decides whether it clears or accumulates is the condition of the pipe it lands on.
Why a cleared drain reblocks
Clearing a drain restores flow. It does not always restore the pipe. Whichever method is used, whatever coats the wall stays there unless the method lifts it off, and next month's material settles onto the same surface. Which method suits your line is a separate question. The deeper issue is geometry. A run that has sagged into a belly holds standing water at its lowest point, and every solid passing through settles into it. A joint that has stepped out of line presents a lip, and a lip catches everything. Neither is affected by cleaning.
When to stop clearing and start looking
Two blockages in the same line within a year is the point where clearing it a third time is the expensive option. A camera survey gives the defect a position and a depth. Sometimes the answer is a single metre of pipe. It is almost never the whole run, and it is almost never your cooking.
Common Questions
Do chemical drain cleaners work?
They can shift a light blockage near the outlet. They do not reach a blockage further down the line, they do not touch a belly or a displaced joint, and repeated use damages older pipe and the seals around it.
How often should a drain need clearing?
A sound domestic drain in normal use should not need clearing on a schedule at all. A commercial kitchen line is different, because the fat load is different, and those are usually jetted on a planned interval.
Is jetting safe on old pipe?
Not always. A cracked or displaced line can be worsened by high pressure. That is why an engineer should look with a camera before jetting any drain that has failed more than once.
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