Septic Backup: What to Do When Your Sinks and Toilets Won’t Drain

Updated October 2026

If more than one drain or toilet is backing up, stop using water right away and call a septic pumper. A single slow sink is usually a clog in that fixture. Several fixtures backing up at once, especially the lowest ones in the house, usually means the main line or the septic tank is blocked or full. D&L Environmental answers septic backups 24/7 at 250-765-0999.

Step 1: Stop the water

Every litre that goes down a drain has nowhere to go but back into the house. Until the problem is fixed:

• Don’t run the washing machine, dishwasher or showers
• Don’t flush toilets
• Shut off the water supply to any toilet that keeps running
• Tell everyone in the house, including guests

If water is pooling on a floor, keep children and pets away from it.

Step 2: Work out whether it’s one fixture or the whole system

One fixture backing up while everything else drains normally is almost always a clog in that fixture’s trap or branch line. A plunger or a plumber usually sorts it out. Skip chemical drain openers: they rarely clear a real blockage, and they’re hard on the bacteria in your septic tank.

Several fixtures backing up together points further down the line. Watch for:

• The lowest drains, such as a basement floor drain or tub, filling first
• Toilets gurgling when another fixture drains
• Sewage odours inside the house or near the tank
• Wet ground or standing water over the tank or leach field

If the tank is full, pumping it relieves the backup right away. If the tank isn’t full and the house still won’t drain, the blockage is in the pipe between the house and the tank, and a plumber is the right call. If the tank fills back up quickly after pumping, or the ground over the leach field stays wet, the field may not be absorbing water. Pumping buys time, but the field itself needs a septic installer.

Step 3: Stay safe around sewage

Raw sewage carries bacteria, viruses and parasites, so treat any backup as a health hazard:

• Wear waterproof gloves and boots if you have to be near it
• Open windows to air out odours
• Wash thoroughly after any contact
• Never open a septic tank or lean into one. Tanks hold toxic gases, including hydrogen sulphide and methane, and old lids can give way.

Leave the pumping to a crew with the right equipment. It isn’t a do-it-yourself job.

Call 911 only if someone is injured or in danger, or there’s a fire. A septic backup is urgent, but on its own it isn’t a 911 emergency.

What happens when our crew arrives

We locate and open your tank, pump it down so the house can drain again, and look over the empty tank for anything visibly wrong. Then we tell you what we found. If the backup was caused by something pumping can’t fix, such as a broken pipe, a failed pump or a leach field that won’t drain, we’ll explain what we saw so you know whether to call a plumber or a septic installer. D&L pumps septic tanks; we don’t install systems or repair pipes, pumps or leach fields. Our guide to what pumping fixes and what it can’t explains the difference.

Why septic systems back up

• The tank is overdue for pumping and solids have blocked the outlet or the field
• Grease, wipes or sanitary products have clogged a line
• Tree roots have grown into a pipe
• Heavy rain or snowmelt has saturated the leach field so it can’t take more water
• Roof, sump or surface water is draining into the system
• Heavy water use, such as many loads of laundry in one day, has overwhelmed the field

How to prevent the next one

• Pump the tank on schedule
• Flush only toilet paper. “Flushable” wipes still clog septic systems.
• Keep grease and cooking oil out of the sink
• Spread laundry over the week instead of doing it all in one day
• Point downspouts and sump discharge away from the tank and leach field
• Keep vehicles, sheds and hot tubs off the field
• Know where your tank lids are. If they’re buried deep, ask us about adding risers so the tank can be reached quickly in an emergency.

More habits that keep a system healthy are in our septic care guide. For an emergency right now, call 250-765-0999, or read about our emergency septic backup service.

Frequently asked questions