Drains
Why Your Drain Keeps Clogging After It Has Been Cleared
One blockage is bad luck. The same blockage twice is a symptom, and clearing it on a schedule costs more than fixing the cause.
Published · 6 min read
Clearing a blocked drain is not difficult. The useful question is whether you will be doing it again in six weeks, and that is answerable from the pattern.
One fixture, or several
Start here, because it splits the problem in half.
One slow fixture, everything else fine. The restriction is local, in that fixture’s trap or the branch line serving it. Grease and food in a kitchen sink, hair and soap in a bathroom one. Clear it and it generally stays clear.
More than one fixture affected at once. The restriction is downstream, in a line that both fixtures share, and the further down it is the more fixtures it takes with it. When a whole floor or the whole house slows down together, you are looking at the main line or the lateral.
That distinction decides where anyone should be working, and it is worth telling us on the phone.
What gurgling is telling you
Gurgling is one of the more informative sounds in plumbing and it usually gets ignored.
It happens when air is dragged through the water sitting in a trap, because it cannot get into the system the normal way through the vents. If your bathtub gurgles when you flush the toilet, those two fixtures are connected downstream, and the restriction is below the point where they join.
That is genuinely useful, because it tells you the problem is not in the fixture you are standing at. It also sometimes points at a venting fault rather than a blockage at all, which is a different repair. Converted houses with added bathrooms, common in the student rentals around Annville, produce a lot of these.
The four things that cause repeats
If a drain blocks in the same place repeatedly, it is almost always one of these.
A sag holding water. A section of pipe that has dropped slightly holds standing water permanently. Solids settle in the low point, and the blockage forms in exactly the same spot every time. This is common on the long laterals under the deeper suburban lots around Palmyra and Annville.
Roots at an open joint. Roots do not break into sound pipe. They find a joint that has already opened, usually in older clay, and grow towards the moisture. Cutting them out restores flow and leaves the opening, so they come back.
An offset or partial collapse. A step inside the pipe where two sections have shifted out of alignment catches everything passing. Cabling cannot help with this at all.
Grease and scale on the wall. Years of deposit narrowing the pipe. This is the one where clearing genuinely works but only briefly, because a cable bores a channel through the middle of the deposit and leaves the rest.
Why hard water makes it worse here
Lebanon County sits on limestone, and the groundwater carries a heavy mineral load as a result.
That matters for drains in a way people do not expect. Scale deposits roughen the inside surface of pipework, and a rough wall gives grease, soap and hair something to grip. A line that would stay clear for a decade in a soft water area starts collecting sooner here.
In the older Lebanon city housing it compounds: cast iron waste pipe is already roughening from rust on the metal side while scale deposits from the water side.
What not to pour down the drain
Prevention is unglamorous and it works.
Grease and cooking oil are the main one. They go down warm and liquid, then cool and deposit on the pipe wall a few feet along. Pour them into a container and bin them instead.
Coffee grounds pack down and accumulate rather than washing through. Fibrous vegetable waste, celery, corn husks and onion skins, wraps around disposal plates and catches. Starchy waste like pasta, rice and potato peel turns to paste. Wipes, including anything labelled flushable, do not break down and are a leading cause of main line blockages.
On chemical drain cleaners: for anything beyond an occasional light clog, they are a poor idea. They generate heat, sit against the pipe wall when they fail to clear the blockage, and on older cast iron and some plastics that is genuinely damaging. They also make the job hazardous for whoever opens the line afterwards. If you have poured some in, say so before anyone starts work.
When to stop clearing and start looking
Our own rule: if we have cleared the same line twice, we will suggest putting a camera down it before doing it a third time.
Repeat blockages in a fixed location mean a sag, roots, an offset or heavy deposit, and none of those are fixed by cabling. A single inspection usually costs less than two more clearances, and it converts a recurring bill into a decision you can actually make.
It also occasionally produces the opposite answer, which is that the pipe is fine and something is genuinely going down it that should not be. That is worth knowing too.
More detail on the clearing itself is on the drain cleaning page. If you are at the point of wanting to see inside the pipe, camera inspection covers what that involves.
