How to Clean a Sump Pump: Step-by-Step Cleaning and Maintenance Guide

A sump pump that has gone a year or two without attention rarely fails quietly. The intake screen silts up, the float snags on the pit wall or the non-return valve sticks, and the first sign is water on the cellar or plant room floor. Regular sump pump cleaning is the cheapest protection against that, and on most domestic and light commercial installations it is a job you can do yourself with basic tools.

This guide deals with the pump unit itself: how to clean a sump pump step by step, which cleaning solutions are safe, how to look after the float switch and non-return valve, how to clean a sump pump without removing it, and how often to do each task. It is written for facilities managers, contractors and property managers, but every step applies to a domestic cellar pump too.

What Sump Pump Cleaning Covers

A submersible sump pump is a simple machine, but six parts have to work together every time the water rises. The diagram shows a typical installation with a tethered float, and our complete guide to sump pumps and how they work covers the basics.

The Six Parts to Clean and Check

Each numbered part has its own cleaning method, covered in the step-by-step section:

1. Intake screen: the perforated base that keeps stones off the impeller, and the part most likely to block.
2. Impeller and volute: the spinning vaned disc that moves the water, and the casing that directs it to the outlet.
3. Float switch: starts and stops the pump. It may be a tethered float, a vertical float on a rod, or an electronic sensor.
4. Non-return valve (check valve): stops water in the pipe falling back into the pit when the pump stops.
5. Discharge pipe: carries the water away; silt or a crushed section cuts flow.
6. Power cable and supply: the cable, plug or connection box, and the RCD protecting the circuit.

Safety Before You Touch the Pump

Start by isolating the electrical supply. Unplug the pump, or if it is hard-wired, switch it off at the fused spur or consumer unit and label the isolator. On commercial sites, follow your lock-off procedure. Never rely on the float being low to keep the pump from starting.

Under BS 7671, socket-outlets rated up to 32 A need additional protection from a 30 mA RCD unless a documented risk assessment by a skilled person decides otherwise, as the IET’s guidance on RCD protection for socket-outlets explains. If it trips when you restore power after cleaning, stop: that usually means an insulation fault needing an electrician or pump engineer.

Treat sump water as contaminated; where rats have access or drains connect, there is a risk of leptospirosis (Weil’s disease). The HSE leaflet on working with sewage sets out the basics: waterproof gloves and eye protection, cuts covered, and hands washed before eating, drinking or smoking.

Deep commercial chambers may be confined spaces under the Confined Spaces Regulations 1997. Work from above using a lifting chain or rope, and only enter with training and a safe system of work.

Tools and Sump Pump Cleaning Solutions

Routine cleaning needs no specialist equipment. Gather these before you isolate the pump:

• Waterproof gloves, eye protection and a head torch.
• A stiff nylon brush, an old toothbrush for the screen slots and a plastic scraper.
• A garden hose, two buckets, a plastic sheet and a wet and dry vacuum.
• A standby pump if groundwater is still coming in while the duty pump is out.

Which Sump Pump Cleaning Solution to Use

Most dirt is silt and slime, which water and a brush will shift. The pump manual takes precedence over this table.

Surface water drains often run straight to a watercourse, so do any chemical cleaning with the pump out of the pit, over a bucket or foul drain, rather than flushing products through the discharge.

Vinegar works on scale because its acetic acid dissolves the calcium carbonate common in hard-water areas; never circulate it neat through the pump. Products sold as a sump pump cleaner, including tablets, mostly target odour; they will not clear a blocked screen or free a stuck float.

How to Clean a Sump Pump: Step by Step

A full clean means lifting the pump out, the only way to reach the underside of the screen and the impeller. These are the eight steps in order.

Lifting the Pump Out Safely

Let the pump run one last cycle to lower the water, then isolate it and photograph how the float, cable and pipework sit so everything goes back the same way. Undo the union or coupling on the discharge pipe and lift the pump by its handle or lifting rope. Never lift a pump by its power cable, which strains the cable entry seal and can let water into the motor.

Cleaning the Intake Screen and Pump Body

Stand the pump on the plastic sheet and hose off loose silt from the top down. Scrape caked sludge from the casing, then work the brush through every slot in the intake screen; a blocked screen is the most common reason a pump runs but moves little water. If the screen unclips, clean both sides, and soak it in the vinegar solution where limescale has narrowed the slots.

Clearing the Impeller and Volute

On many submersible pumps the impeller is visible through the intake once the screen is off. With the power still isolated, pull out fibres, stones or wipes with a plastic tool, then turn the impeller gently by hand; it should spin freely without grinding. Only dismantle as far as the manufacturer’s manual allows, as opening the motor or seal chamber is a workshop job and can void the warranty. A chipped or rubbing impeller means the pump needs servicing.

How to Clean a Sump Pump Float Switch

A float that cannot move leaves the pump unable to start, however healthy the motor. Clean it according to its type:

• Tethered float: wipe the float and cable, check for cracks or kinks, and confirm the tether length, which sets the on and off levels, has not changed.
• Vertical float: clean and descale the rod, then slide the float by hand to confirm it moves freely.
• Electronic sensor: wipe slime and scale off the sensor face as the manual directs, since deposits can cause false starts.

Our float switch guide covering types, wiring and setting levels goes into more detail. If the float is cracked or waterlogged, replace it with one from our range of replacement float switches rather than trying to seal it.

Checking the Non-Return Valve

A leaking non-return valve lets the water in the pipe fall back into the pit each time the pump stops, so the pump moves the same water again and cycles far more than it should. Open the valve if it has an access cover, clean silt from the flap or ball and its seat, and check the flow arrow points away from the pump. Some installations have a small air-release hole between pump and valve to prevent airlocks; clear it with a piece of wire.

Flushing the Discharge Pipe

Run the hose through the pipe to wash out settled silt, then check the outlet is clear of leaves and soil and the run has no crushed or sagging sections, as any restriction adds to the head the pump works against. If flow is still poor with a clean pump, the pipe may be too small; our guide to choosing the right pump discharge pipe size explains how pipe diameter affects flow and friction losses.

Refitting and Testing the Pump

Lower the pump onto a firm, level base, not silt, and make sure the float cannot touch the wall, pipework or cable anywhere in its travel. Reconnect the union and restore power.

Fill the pit slowly with clean water. The pump should start at the switch-on level, discharge strongly and stop at the switch-off level, with no water draining back down the pipe. Watch at least two full cycles, and do not run the pump dry: many submersible pumps rely on the surrounding water to cool the motor and lubricate the shaft seal. Record the date and findings in your maintenance log.

How to Clean a Sump Pump Without Removing It

Where a pump is rail-mounted or rigidly plumbed, or you only need a quick clean between services, you can do a useful job with it in place:

1. Isolate the power and label the isolator, exactly as for a full clean.
2. Brush the visible screen and casing with a long-handled brush, and wipe the float.
3. Hose the pump and float down, then vacuum out the loosened silt.
4. Restore power and run several cycles with clean water.
5. Watch the float’s full travel and check the non-return valve holds.

You cannot reach the underside of the screen or the impeller this way, so treat it as an interim clean and lift the pump out at least once a year.

What About the Sump Pit?

The best time to deal with the pit is while the pump is out. A clean pump dropped back onto a layer of sludge soon clogs again, so at the very least vacuum out loose silt and stones before refitting.

Scraping the walls, clearing hardened black sludge and dealing with odour in the chamber is a separate job with its own method. Our step-by-step guide on how to clean a sump pit, including sludge removal and odour control covers it in full.

Sump Pump Maintenance Schedule

The Sump and Sewage Pump Manufacturers Association (SSPMA) in the US suggests cleaning the intake screen monthly where a washing machine discharges into the sump, every three to four months where it does not, and removing and cleaning the pump and pit once a year. Your pump manufacturer’s manual takes precedence where it gives different intervals.

Our guide on preparing your pumps for winter covers frost protection for exposed pipework. On commercial sites, add these tasks to your planned maintenance schedule, keep a logbook for each pump, and confirm that duty and standby pumps both run.

Troubleshooting: Symptoms, Causes and Fixes

Use this table to work out whether cleaning will fix a fault or the pump needs an engineer.

A pump that runs constantly in wet weather even when clean is often simply too small for the inflow. Our guide on working out what size sump pump you need walks through the flow and head calculation.

When Sump Pump Maintenance Is Not Enough

Cleaning fixes silt, scale and a stuck float. It does not fix electrical or mechanical wear.

A damaged power cable is not a DIY repair: manufacturers’ manuals typically require it to be replaced by the manufacturer, their service agent or a similarly qualified person. If the pit takes wastewater from toilets or kitchens, a standard sump pump is the wrong tool; our comparison of sewage pumps and sump pumps explains when you need a unit designed for solids. On critical commercial sites, a like-for-like spare on the shelf turns a failed pump into a quick swap rather than a flood.

Recommended Sump Pumps and Spares from AES Rewinds

If cleaning shows your pump is past its best, our full range of submersible sump pumps covers clean and dirty water duties, and sump pumps with integrated float switches make a simple swap where your current pump has a built-in float. For discharge runs, see our hose and pipework accessories.

Unsure whether to repair or replace? Contact our team with the make, model and symptoms and we will advise.

Frequently Asked Questions

How Often Should a Sump Pump Be Cleaned?

Clean the intake screen every three to four months, or monthly if a washing machine drains into the sump, and do a full clean once a year, unless the manual says otherwise. See the sump pump maintenance schedule.

What Is the Best Sump Pump Cleaning Solution?

Clean water and a stiff nylon brush handle most jobs. Use diluted vinegar for limescale and diluted bleach only to disinfect, never together. The cleaning solutions table covers each option.

Can You Clean a Sump Pump with Vinegar?

Yes. A 1:1 mix of white vinegar and water dissolves limescale on the screen, float and casing. Apply it with the pump out of the pit and rinse it off thoroughly.

How Do You Clean a Sump Pump Without Removing It?

Isolate the power, brush the screen and float in place, vacuum out loosened silt, then run several cycles with clean water. You still need a full clean once a year; see the in-place cleaning steps.

How Do I Clean a Sump Pump Float Switch?

With the power isolated, wipe the float and cable, descale a vertical float rod if needed, and check the float travels freely without touching the wall or pipework. More detail is in the float switch cleaning section.

Why Does My Sump Pump Keep Running After Cleaning?

The usual causes are a float snagged in the raised position, a leaking non-return valve letting water fall back, or more inflow than the pump can handle. The troubleshooting table matches each symptom to its likely cause.

Key Takeaways

Routine sump pump cleaning costs far less than a flooded basement or plant room. The points that matter most:

• Isolate and label the supply first, and stop if the RCD trips afterwards.
• Clean the intake screen and float every few months, not just annually.
• Water and a brush do most of the work; never mix vinegar and bleach.
• A leaking non-return valve causes short-cycling, so check it every time.
• Test through two full cycles with clean water, never dry.

Related Articles

• How to Clean a Sump Pit: clearing sludge, scale and odour from the chamber itself.
• Float Switch Guide: float types, wiring and setting switch levels.
• Basement Sump Pump Guide: choosing and installing a pump for cellars and basements.
• What Size Sump Pump Do I Need?: sizing on inflow and head.
• How to Prepare Your Pumps for Winter: frost protection for pumps and pipework.