Why Are My Drains Backing Up Every Time It Rains? (SA Guide 2026)

Quick answer

If your drains gurgle and overflow whenever it rains, you almost certainly have stormwater entering your foul sewer line - either at a cracked gully, root-damaged pipe, or an illegal downpipe connection. In most SA municipalities, the pipe from your boundary to the house is YOUR liability; from the boundary to the main is the council's.

The three causes (in order of likelihood)

1. Blocked or cracked gully trap (60% of cases) That open dish-shaped drain outside the kitchen / bathroom is the gully. Leaves block the grid, water pools, then floods. Cracks let rain seep into the pipe network. Fix: clear, then re-seal with quick-set cement (R180 DIY) or call a drain specialist.

2. Tree roots in clay pipes (25%) 1960s-1980s SA homes use salt-glazed clay pipe in 1m sections. Roots find the joints, then rain pressure-tests the blockage. Symptom: backups only with heavy rain, fine otherwise. Fix: jetting (R1,400-R2,800) or pipe relining (R1,200/m).

3. Illegal downpipe-to-sewer connection (15%) Some 80s-built homes ran roof downpipes straight into the foul sewer. Heavy storm = roof acres of water dumped into a 110mm pipe designed for 5 toilets. Fix: disconnect the downpipe, route to garden or stormwater. Council fine if caught: R15k+ in Joburg, more in Cape Town.

Who pays

• Inside your boundary: you
• Council main backing up into your yard: them, and you can claim for damage with photos + dated reports

When to act now

If sewage is on the floor: stop using water in the house, ventilate, and book emergency blocked drains in Johannesburg, Cape Town, or Durban.