A tap is the point where a smaller pipe enters a larger one: a branch line into a building drain, a lateral into the street main, a floor drain into a collector. Done properly, with a wye or a tee fitting, the connection is smooth and the camera passes it with barely a change in the picture. Done badly, by cutting a hole in the larger pipe and pushing the smaller one through, the branch protrudes into the bore, catches every wipe and root that passes, and becomes a blockage that no amount of cabling cures. Protruding taps are among the most common defects in municipal inspections and are easy to find in private laterals once you know the shape.
Quick answer: a sound tap shows on camera as a smooth opening in the side wall of the pipe, usually at a moulded fitting, with the branch pipe flush with or slightly recessed from the main bore. A protruding tap shows the end of the branch pipe standing into the bore, often with a ragged hole around it, debris caught on it and roots entering at the gap. A broken tap shows a shattered opening with pieces of pipe missing. A hammer tap, cut without a fitting, shows a rough hole with the branch loosely inserted. Protruding and broken taps need a spot repair or a robotic cutter; a sound tap is simply recorded.
Where taps are found
In a residential lateral, the taps are where branch lines join the building drain inside the house and where the lateral joins the main at the street. In a commercial building drain, every floor drain, floor sink and fixture group taps in. In a main, every lateral is a tap, which is why mainline inspections spend so much time on them. The connection at the street is often the worst-built joint on the whole lateral, because it was made from a trench against a live main by whoever laid the house connection decades ago. Locating the connection at the main covers finding it from the surface.
What a good tap looks like
A wye or a tee fitting, with the branch entering at an angle or square and the inside of the fitting smooth. The opening is round or oval and its edges are the fitting’s own moulded edges. Nothing stands into the bore. In clay and cast iron mains the fitting may be a factory wye; in newer plastic a moulded tee or a saddle fitting properly solvent-welded with the branch cut flush. On camera the picture shows a side opening and continues without interruption.
What a bad tap looks like
Protruding. The branch pipe end stands into the main bore by anything from a fraction of an inch to most of the diameter. Paper, wipes and roots hang from it. The camera head bumps it. The hole around it is often ragged. This is the hammer tap, cut with a hammer and chisel and the branch pushed in, or a saddle fitting with the branch cut too long. Broken. The main pipe is shattered around the tap, with pieces missing and soil visible, usually from the same hammer. Intruding seal. Mortar, grout or sealant squeezed into the bore when the tap was made, forming a hard lump at the opening. Each catches debris and each is a blockage that returns. Recurring clogs at the same spot are very often a bad tap.
Roots and infiltration at taps
A tap is a hole in the pipe sealed by whatever the installer used. When that seal fails, which it does, the tap becomes the main root and water entry on the line. On camera the signs are roots growing in around the branch pipe, a stain below the tap, and in wet weather water running from the gap. A tap with roots is a tap whose seal has gone, and cutting the roots without resealing the tap is temporary. The infiltration guide covers reading the water entry.
Repair options
A protruding tap in an accessible line is excavated and rebuilt with a proper fitting. In a main, a robotic cutter can trim the protrusion flush without digging, which is the municipal standard, and a lateral connection can then be sealed with a top-hat liner. In a private lateral, the connection at the main is usually dug and rebuilt as part of any lining job, because the liner cannot be run through a protruding tap. A broken tap is always a dig. The camera’s counter reading and a sonde locate at the tap are what make the dig a hole rather than a trench. Reinstating laterals after lining explains how taps are reopened through a new liner.
What to record
The counter reading at the tap, the direction it enters from, how far the branch protrudes, whether the opening is ragged or broken, and whether roots or water are entering. A still with debris on the protrusion is the picture that explains the recurring blockage to a customer.
Common questions
Why does my line block at the same point every few months?
Often a protruding tap. Camera it; the branch end will be visible with debris on it.
Can a tap be repaired without digging?
In a main, a robotic cutter and a top-hat liner can. In a small private lateral, usually not.
Is a saddle tee a bad tap?
Not if the branch was cut flush and the saddle sealed. A saddle with the branch pushed through into the bore is the problem.
Related guides
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