Question and photo say it all really. There is a gully trap for the grey wastewater at the back of our multi-unit building that is about 120 years old. The trap seems to be made of fired clay and has a large crack.

Cracked clay trap

Is this going to be a significant problem, and can it be repaired without needing to excavate the concrete and replace the whole thing? I was thinking using a flexible waterproof sealant to fill the crack.

(I am in New Zealand).

  • It should work since it is low pressure use. The problem with sealers is that the surface must be clean to almost like new and they need time to completely set, usually more than just a couple of hours.
    – crip659
    Mar 19, 2023 at 10:52
  • Where does the clay end and the concrete begin? Because it looks to me like a concrete "bowl" above the VCP bell.
    – Huesmann
    Mar 19, 2023 at 12:20

1 Answer 1


Fixing it with a sealant will be fine. Just scrub it well and dry it first. Replacing it will be a big job.

However, gully traps normally have a grill to stop leaves, etc from going in and blocking the pipe.

  • Thanks for the comment, I will give it a good scrub clean and seal. As for the grate, I will see if I can purchase a new one. Thanks for the answer. Mar 23, 2023 at 6:41

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