The overflow relief gully — usually shortened to ORG — is one of the most important and least appreciated parts of your drainage system. It is the grated outlet, typically near an outside wall, sitting slightly below the level of your indoor fixtures.
Its job is simple: if the sewer line blocks and waste backs up, the ORG is engineered to be the lowest escape point. The loose grate lifts or the water spills over the rim, releasing the backup outside your home. Without a functioning ORG, that same sewage rises through the lowest indoor outlets instead — usually the shower, floor waste or toilet.
For the ORG to protect you, a few rules matter:
- Never seal, glue down or pave over the grate. It has to be able to release water freely.
- Keep it clear of garden beds, mulch, pot plants and landscaping build-up.
- Keep the level difference. If paving or decking raises the ground around it above indoor floor level, the protection is lost — a common issue after renovations.
- Water sitting in or lifting the grate is a warning sign that the main drain is partially blocked. Treat it as an early alarm.
If your ORG regularly weeps, smells or overflows, the main sewer drain needs attention promptly — it is telling you a full backup is close.