Sewage Pump Alarm Going Off? What to Do in the First Hour

If a sewage pump or treatment plant alarm is going off, stop using water in the property straight away and check whether the pump or plant still has power. The alarm almost always means one of two things: the chamber is filling faster than it is being emptied, or a pump or air blower has stopped. Either way, every flush and every shower from now on goes into a chamber that is not emptying, so cutting water use is what buys you time.

What the alarm is actually telling you

Most domestic pumping stations and package treatment plants have a float switch set above the normal working level. When sewage reaches that float, the alarm sounds. It is a warning that the level is too high, not that sewage is already escaping.

You will usually find one of three set-ups behind the alarm. A sewage pumping station collects waste from a basement flat, a garden annexe or a property below the level of the sewer, and pumps it up through a rising main to a gravity drain. A package treatment plant treats sewage on site and relies on an air blower to keep the bacteria working. A sump pump in a basement or lightwell handles groundwater and surface water rather than sewage, but its alarm means the same thing: water is coming in and not going out.

The alarm panel is usually a small box on a wall inside the house, in a garage or on a post near the chamber. Many have a buzzer, a red light and a mute button. Muting the buzzer is fine. Muting it and forgetting about it is how a high-level alarm turns into sewage in the garden or the basement.

The first checks you can do safely

Stop water use, then check power. A tripped breaker or a blown fuse on the pump's spur is one of the most common reasons an alarm goes off, and it is the one thing you can put right yourself.

• Tell everyone in the building. In a house split into flats, a basement pump often serves more than one household. Ask everyone to stop flushing, showering and running the washing machine until it is sorted.
• Look at the consumer unit and the pump's fused spur. If a breaker has tripped, reset it once. If it trips again, leave it off. A breaker that will not stay on usually means a pump motor fault or water in the electrics, and repeated resets can damage the pump further.
• Listen at the chamber. If the pump is humming but the level is not falling, the impeller may be jammed with wipes or rag, or the rising main may be blocked. If it is silent with power on, the pump or its float switch has failed.
• Do not open the chamber and reach in. Pumping station chambers can hold sewage gases, the lids are heavy, and the pump is live equipment. Looking at the level from the edge is fine; putting hands or tools in is a job for someone with the right kit.
• Take a photo of the panel and any labels. The make of the pump or plant, and any service company sticker, saves time when you call.

How long you have before it overflows

It depends on how much storage the chamber has above the alarm level and how much water is still going into it. With water use stopped, many systems will hold for hours. With a household still flushing and showering, some will overflow the same evening.

Current Building Regulations guidance expects a domestic pumping installation to hold roughly a day's inflow as emergency storage, so that a power cut or pump failure does not flood the property straight away. Older and home-built installations often hold far less, and plenty of London basement conversions were fitted with small chambers that fill quickly. If you do not know how old or how large your system is, assume the storage is small and treat it as urgent.

Sewage overflowing from a pumping station usually comes out at the lowest point it can reach: the chamber lid itself, a basement shower tray or floor gully, or a toilet on the lowest floor. If the level is visibly near the lid, or water has started backing up into the lowest fittings, it needs attention tonight rather than tomorrow.

Pump fault, blockage or full plant: working out which

The quickest guide is what the pump is doing. A silent pump with power points to a failed pump or float. A running pump with a rising level points to a blockage. A treatment plant alarm with a quiet blower points to an air supply fault, not a full tank.

Blocked impeller or rising main. Wipes, sanitary items and fat are the usual cause. They wrap around the impeller or settle in the rising main where it climbs to the gravity drain. This is a drainage job: the chamber is pumped down, the obstruction cleared, and the rising main and downstream drain are jetted so the pump has somewhere to discharge to.

Failed pump or float switch. Pumps wear out, and float switches stick when they are coated in grease. The chamber still needs pumping down so the level is safe, but replacing the pump or its controls is work for a pump engineer or the installer's service company. We will tell you if that is what we find, rather than charge for a clearance that will not fix it.

Treatment plant blower failure. If a treatment plant's alarm is linked to the air supply rather than the level, the tank may not be full at all. The blower needs repairing by whoever services the plant. A tanker is only needed if the level is also high or the plant is overdue for desludging.

What an emergency drainage call-out can do tonight

An engineer can pump the chamber down by tanker so the property is usable again, clear any blockage in the pump or rising main, and jet the drain the pump discharges into. That removes the immediate risk even if the pump itself needs replacing later.

Tankering a pumping station or treatment plant is the same service as emergency septic tank and cesspit emptying: a vacuum tanker draws the chamber down and takes the waste away for licensed disposal. If the problem turns out to be a blocked downstream drain, it is cleared with rods or high-pressure drain jetting, and a camera check confirms the pump has a clear run to discharge into.

Our rates follow the clock. Work attended between 7am and 5pm is charged at the standard rate, 5pm to midnight at the evening rate, and midnight to 7am at the night rate. Current figures are on the pricing page, and the price is agreed on the phone before anyone travels. If the level is falling after you stopped water use and nothing is escaping, booking for first thing in the morning is a reasonable choice.

Stopping the alarm coming back

Most repeat alarms come from what goes into the system. A pump will handle toilet waste and paper; it will not handle wipes, sanitary products, cotton buds or cooking fat for long, even if the packet says flushable.

Put a clear note in the bathroom of any basement flat or annexe that drains to a pump, particularly if it is let or used by guests. Ask whoever services the pump or plant for a maintenance visit at the interval the manufacturer recommends, and make sure the float switches are cleaned at the same time. In managed buildings, the same logic applies as with any shared drain: the pumping station belongs to whoever owns the common parts, and our note on handling a blocked drain in a managed building out of hours covers who to call first.