Maintenance and Cleaning of the Backflow Valve

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Maintenance and cleaning of a backflow check valve – complete practical guide

The backflow check valve is one of those devices that most homeowners only remember when it stops working – and that is usually at the worst possible moment, when the sewage starts flowing where it shouldn't. Yet it is one of the few components of the sewage system that requires regular, but by no means complicated, maintenance. If you take care of it systematically, it will last for decades without any problems. If you ignore it, it may cause damage worth thousands of euros – a flooded basement, ruined floors, equipment replacement. This article is about how to properly and regularly inspect, clean, and maintain the valve in full functionality.

Why regular maintenance of the backflow valve is absolutely essential

The backflow valve operates on a simple mechanical principle: the valve closure (a disk or "float") opens in the direction of the outflow and closes under reverse pressure. This very simplicity is its strength, but also its weakness – any piece of solid waste, any fat or fiber that gets caught on the moving parts can prevent proper closure. And a valve that doesn't close won't protect you from anything.

From experience, I know that the most common cause of failure of a backflow valve is not a mechanical fault of the part itself, but neglected maintenance. Sewage water carries with it fats, fibers from textiles (toilet paper, wet wipes), fine sediments, soap fragments, and various organic residues. These substances gradually settle on the body of the valve, on the pivot axis, and especially on the sealing surface. If the seal does not close completely, even a small pressure from a flooded public sewage system will be enough for water to start flowing backward.

In practice, I recommend inspecting the valve at least twice a year – ideally in spring after winter and in autumn before winter. In households with a larger number of residents, or if the building houses a restaurant or business with higher wastewater production, inspections should be quarterly. You can write the exact dates directly on the manhole cover or in a home inspection diary – such a simple record will save you a lot of trouble.

Preparation for cleaning – what you will need and safety rules

Before the actual cleaning, it is important to prepare everything you need. Working with a sewage system is not dangerous if simple rules are followed, but certain hygiene rules must be respected.

Tools and materials:

Chemical-resistant rubber gloves (not thin latex ones – thicker household rubber gloves)
Protective goggles (splashing water from the sewage is unpleasant)
A flashlight or headlamp (manholes are dark)
A flat screwdriver and possibly a wrench (depends on the type of closure of the inspection cover)
A plastic scraper or an old knife (for mechanical removal of deposits)
An old toothbrush or a stiff brush
A bucket with warm water
A degreasing agent (solid soap or regular dish soap – not aggressive lyes)
A cloth or paper towels
A disinfectant at the end

Safety rules: Never clean the valve when water is running from taps, the washing machine, or the dishwasher in the house. Wastewater could escape through the open inspection opening of the valve during cleaning. Ideally, clean in the morning before the day starts, when the system is inactive. If the valve is installed in a manhole, make sure you have a stable access – do not recklessly enter a deep manhole without sufficient lighting.

How to get to the valve – access via a manhole or inspection opening

Inline backflow valves, such as those available at atria.sk – specifically inline backflow valve DN 110, inline backflow valve DN 125, or inline backflow valve DN 200 – are designed precisely to allow easy access. The valve body has an inspection cover that can be unscrewed or unfastened, giving you direct access to the internal mechanism without the need to disassemble the entire assembly from the piping.

If the valve is installed in a garden manhole, you must first open the manhole cover. This depends on the type of manhole: for a smaller diameter, a manhole cover 315 is used, for a larger one a manhole cover 400. Both covers are designed to be easily opened with a simple tool, but at the same time sufficiently tight to prevent dirt or rainwater from entering. Place the cover in a safe location – a heavy plastic or cast iron cover can damage the valve or the piping if it falls into the manhole.

Step-by-step cleaning of the backflow valve

Cleaning the valve is a straightforward process that any resourceful homeowner can manage without special knowledge. It requires only patience and thoroughness.

Step 1: Visual inspection from the outside

Before opening the inspection cover, look at the outside of the valve body. Check for visible cracks, whether the inspection cover nuts are cracked or corroded, and whether water is leaking from the valve along the pipe body. Any visible damage to the seal between the valve and the pipe is a sign that cleaning alone is not enough – the tightness of the connection must also be addressed.

Step 2: Opening the inspection cover

The inspection cover on the body of the backflow valve is usually secured with screws or nuts. Unscrew them and carefully lift the cover. Don't forget to place a cloth or a small bucket underneath the cover – there is always some water left in the valve body that will flow out when opened. Place the cover on a clean surface and immediately check the gasket: it should be elastic, without cracks and without hard spots. If the cover gasket is hardened, cracked or deformed, this is the ideal time to replace it (a standard rubber gasket strip or profiled gasket – depending on the specific valve model).

Step 3: Inspection and removal of the valve disc

In most backflow valves, the disc (the valve itself) is removable. It is located on the pivot axis and can usually be flipped or removed without tools – simply lift it and pull it out of the body. Some models have a safety pin or clip – this must be carefully removed with a screwdriver.

After removing the disc, inspect it thoroughly. Common findings from practice include:

A thin layer of fat or soap scum on the surface of the disc
Fibers from toilet paper or fabric caught around the pivot axis
Thicker layers of organic sludge on the lower edge of the disc
Corrosion or rust on the metal axis (in older metal valves)
Cracks or permanent deformations of the disc (a signal for replacement)

Step 4: Mechanical cleaning of the inside of the valve body

When the disc is removed, use a flashlight and look inside the body of the valve. A sediment is almost always found at the bottom of the body – a harder layer of sludge, sand, sometimes also fibers or small solid objects (stones, fragments). Remove these deposits with a plastic scraper or an old knife, then wipe with a cloth. Never use metal tools for this, as they could scratch the sealing surface.

Clean the sealing surface (the seat, where the disc sits when closing) especially thoroughly. Even a small grain of sand or a fiber here can cause a leak. To clean the seat, use a firm sponge or a toothbrush with warm water and a degreaser, then rinse with clean water.

Step 5: Cleaning the valve disc

Rinse the disc in a bucket of warm water, then clean it with a sponge. If there is a thick layer of fat on it, a dishwashing detergent or solid soap will help – let it work for 5 minutes, then scrub with a sponge. Clean the pivot axis from deposits and fibers – this is a key point, because if the axis does not rotate freely, the disc may not open or close completely. Finally, rinse the disc with clean water and dry it with a cloth.

Step 6: Checking the seal and lubricating the axis

Before inserting the disc back, check the rubber seal around the disc. It should be homogeneous, elastic and undamaged. It is advisable to lubricate the pivot axis with a small amount of silicone lubricant (not oil-based – it damages rubber). Silicone lubricant ensures smooth movement of the disc and also protects the rubber seal from drying out.

Step 7: Reassembly and functional test

Insert the disc back onto the axis, secure it with a clip or pin (if applicable). Place the gasket on the cover – if you replace the gasket with a new one, apply a thin layer of silicone paste to it, which will improve its sealing. Fasten the cover with screws, but do not over-tighten – plastic can crack under too much force. Tighten gradually in a cross pattern, evenly.

The functional test is simple: turn on the water at one of the drains (sink, shower) and listen whether the valve "clicks" during water flow, which is normal, and then check whether water is dripping from the cover of the valve. If only drops are dripping, try tightening the cover a little more – if it still leaks after tightening, the gasket is likely damaged and must be replaced.

Cleaning agents – what to use and what to definitely avoid

When cleaning a backflow valve, the rule applies: less is more and aggressiveness is not worth it. Rubber seals, plastic parts and even some metal axes are sensitive to aggressive chemicals.

What you can safely use:

Warm water (not boiling – for plastic parts, the maximum is around 60 °C)
Dishwashing detergent – gentle degreasing without damaging the rubber
Hard soap
Vinegar solution (1 : 3 with water) – effective for lime deposits and light sludge
Baking soda – mechanical removal without scratching
Silicone lubricant for the axis and seal
Disinfectant (e.g. Savo or similar) for final disinfection – but only diluted and rinsed with water

What you must never use:

Lyes and acids (damage rubber seals, can damage plastic parts)
Acetone or solvents (dissolve plastic surfaces)
Abasive cleaning powders or wire brushes (scratch the sealing surface)
High-pressure water jets directly into the valve body without covering (you can wash out the seal)
Oil-based lubricants (vaseline, motor oil) on rubber seals – rubber swells and tears

From our experience: homeowners sometimes try to solve flap problems by flushing with a strong jet of water from a hose under pressure. If the pressure is too high and the inspection cover is not properly sealed, you may flush the gasket out of the cover or even push the disc off the shaft. Result: the flap is completely disassembled, the gasket is in the shaft, and the disc is somewhere in the pipe. A water jet is suitable only for final rinsing after mechanical cleaning.

Special situations – heavy deposits, biological growth and sludge

Sometimes a customer comes in saying they have never cleaned the flap – let's say five, seven, even ten years. In such cases, the flap is usually so clogged that the disc is practically blocked in a certain position and the gasket is as hard as wood. The procedure is a bit different in these cases.

First, let the inside of the flap soak – pour diluted vinegar (or a special limescale remover designed for plastic pipes) into the body of the flap and let it work for 30 to 60 minutes. Biological deposits and lime deposits will soften and go down more easily. Then clean mechanically with a sponge and a plastic scraper. If the disc is so clogged that it cannot be removed – never press it with excessive force. Rather, let the solution work longer. For heavy biological growth (green-black slime), use diluted disinfectant, let it work for 20 minutes, then clean with a sponge.

In extreme cases, when the disc is physically damaged (deformed, cracked) or the disc gasket is completely degraded, the only solution is to replace the entire flap or at least the internal parts (disc + gasket). Some manufacturers sell service kits – disc and gasket separately – which is a more economical alternative to replacing the entire body. Before purchasing, check whether the specific model allows this option.

Frequency and schedule of maintenance according to type of installation

Not every household has the same load on the sewer. Therefore, it is reasonable to set the maintenance frequency according to actual use:

Type of operation	Recommended cleaning frequency	Note
Family house, 2–4 people	2× per year (spring and autumn)	Standard recommendation
Family house, 5+ people	3–4× per year	Higher volume of wastewater
Restaurant, kitchen operation	Every 2 months	High fat content
Recreational cabin (seasonal)	Before opening the season + after closing	Risk of gasket drying out
Basement with WC and shower	3× per year	Flap carries full load

In addition to regular cleaning, it is advisable to check after each heavy storm (when sewer overflows may occur) whether the flap is functioning properly. In practice, this means simply looking into the shaft, making sure the inspection cover is intact and dry, and checking the area around the flap for any moisture or water seepage.

Regular inspection without disassembly – what to watch from the outside

Between cleanings, you can perform quick visual inspections without disassembling the flap. These inspections give you a good idea of the condition of the device and early detection of signs of problems.

What to watch during a visual inspection:

Moisture or water droplets on the outside of the flap body – a sign of gasket failure
Odor from the shaft or from the area around the flap – may indicate a leaky flap allowing gases from the sewer to pass through
Noises from the flap when not in operation (when nothing is draining) – tapping or creaking may indicate backflow or a rapidly worn shaft
Condition of the inspection cover – cracks, loose screws, deformation
Condition of the shaft cover – must not be cracked or shifted, otherwise there is a risk of foreign objects or rainwater entering the shaft

If you find anything suspicious during a visual inspection, don't leave it "for later". A flap that leaks quietly will most likely let you down exactly when it's most important – during a sewer backup during a heavy rainstorm.

When to replace the flap instead of cleaning

Cleaning and maintenance have their limits. There are situations where repair and cleaning are counterproductive and the only sensible solution is to replace the flap with a new one. You know this from practice – every experienced plumber knows when it makes sense to rehabilitate a flap and when it's time to say enough.

Signs that the flap needs to be replaced:

The flap body is cracked or deformed – this is not a repairable condition
The disc rotation shaft is corroded or broken
The disc is permanently deformed (e.g. compressed by backwater pressure) and does not seal tightly on the seat
The seat gasket (inside the flap body) is physically damaged or missing
The flap leaks repeatedly despite cleaning and disc replacement – the seat is damaged
The flap is older than 15–20 years (for plastic ones), or 10–12 years under higher loads
After a flood event, where the flap held pressure for a long time

Replacing a flap is much simpler and cheaper than many people fear – for through-flow flaps, it is enough to disconnect the pipe on both sides (usually using rubber gaskets or couplings), remove the flap and install a new one. A detailed replacement procedure can be found in the article Installation of a sewer backflow flap step by step in this Knowledge Center.

Impact of Installation Quality on Maintenance Effort

From experience, I know that valves installed in the wrong position or in an unsuitable location are much harder to clean and wear out faster. Proper installation is half the success of long-term trouble-free operation.

A check valve should always be installed horizontally (or with a slight slope in the direction of the outlet), never vertically. Vertical installation causes the disc to have no natural position of "closed" or "open" – when water is draining, it has to be kept open by the water pressure alone, which is a much greater load on the mechanism. In a horizontal position, the disc drops into the closed position by its own weight, which is the ideal state.

The inspection cover should point upwards or at a 45° angle to always be easily accessible. Valves built in directly under the ceiling or hidden behind tiling are almost impossible to clean – and therefore are either not cleaned at all or require a plumber with an expensive service call. For more information on the correct selection of location and type of valve, see the article How to Choose the Right Sewer Check Valve – Diameter, Type and Placement.

Another important factor is access to the manhole. If the valve is installed in a manhole in the garden, the manhole cover should always be easy to open and not overgrown with grass or shrubs. You should also check the manhole cover during each valve maintenance – a cracked cover does not protect the manhole from rainwater or mechanical damage.

Cleaning a Valve in a Manhole – Specifics and Differences

When the valve is installed in a garden manhole (a common situation in new buildings), cleaning has several differences compared to a valve directly on the pipe in the basement. The manhole is deeper, access is a bit more complicated, and the lighting is worse. Here are a few practical tips from field experience:

Always work with good lighting – a headlamp is ideal because you have free hands
Never enter a manhole deeper than 1 meter alone and without safety measures – the risk of falling is real
Let the wastewater that flows out when opening the cover drain to the bottom of the manhole – if the amount is large, pump it out with a small bucket or a suction pump
Keep your tools in a small bucket that you lower into the manhole on a rope – it will save you a lot of nerves searching for tools in the dark
Conclusion: always close the manhole with a properly placed cover – a loosely placed cover can easily fall out or be carried away by heavy rain

Tips for Extending the Lifespan of the Valve Beyond Cleaning

Aside from direct maintenance, you can also extend the lifespan of the valve with proper habits in daily sewer use. These tips may seem trivial, but they have a real impact in the long run:

Do not pour cooking oils and fats into the drain – a solid layer of fat on the valve disc is the most common cause of a non-functional seal
Do not use wet wipes or tampons in the toilet – fibers get caught on the valve shaft
Install a strainer on the drain in the shower or bathtub – it catches hair and fibers before they reach the valve
Pour hot (not boiling) water down the drain once a month – a simple measure that flushes away fat deposits before they can settle
Before a long absence from the house (holiday, winter closure of a cabin) perform a valve inspection – dry rubber during the break can crack or deform

Most Frequently Asked Questions (FAQ)

How do I know that my check valve is not working properly, even if nothing is flooded?

The most reliable sign is a weak smell of sewer gases in the basement or cellar – these gases penetrate through the leaky valve from the drain. Another sign is if you hear gurgling or bubbling in the sewer waste when using the toilet or shower – this may indicate that air is passing back through the poorly sealing disc. To directly test the functionality, open the inspection cover and check if the disc is closed in its resting state and fully seated on the sealing surface. If the disc moves easily and returns to the closed position, the valve is in good condition.

Do I need to grease the valve shaft again every spring, even if it seems to be in good condition?

Yes, I recommend greasing the shaft with silicone lubricant during each cleaning, at least twice a year. Silicone lubricant slowly washes away with wastewater, and the rubber of the shaft dries out and hardens without lubrication. It is just an extra minute of work that significantly extends the life of the shaft and ensures smooth disc movement. Do not use other types of lubricants – oil-based products damage the rubber.

Can I clean a DN 200 valve in the same way as a DN 110 valve?

Yes, the procedure is essentially the same. The difference is only in the size of the parts – the disc in a DN 200 valve is significantly larger and heavier than in a DN 110 valve, so be careful when removing the disc and make sure it does not fall into the body of the valve. In large diameters (DN 200), there may also be more sediment in the body of the valve – cleaning may take longer, but the procedure is the same.

What should I do if the valve does not seal immediately after cleaning and reassembly?

The most common cause is an improperly seated cover gasket or a remaining piece of dirt on the seating surface. Open the valve again and inspect the seating surface – using a flashlight, look for a fiber, a grain of sand, or a small piece of dirt that is preventing the disc from fully seating. Thoroughly clean the seating surface, apply a thin layer of silicone to the disc gasket, and reassemble. If the problem persists, the disc or the seating gasket is likely damaged and needs to be replaced.

Can I use drain cleaning tablets or chemical agents (e.g., for pipe descaling) together with a check valve?

Common biological drain cleaners (tablets with enzymes) are harmless to the valve. Chemical descalers based on citric acid are also acceptable in low concentrations if properly diluted. However, never use concentrated lyes (e.g., drain unblockers containing NaOH in granulate form) – these can cause permanent damage to the rubber gasket and plastic disc. Always read the instructions before using a chemical agent to ensure it is compatible with PVC/PP pipes and rubber gaskets.

Do I need a professional company for valve maintenance, or can I do it myself?

Regular maintenance of a check valve can be handled by any technically capable homeowner – the procedure is simple, requires minimal tools, and the risk of error is low if you proceed carefully. I recommend calling a professional when the valve shows signs of failure that cannot be resolved by cleaning (e.g., a damaged seating surface, a cracked body), or when the valve is installed in a hard-to-reach location. Replacing the valve with a new one can also be done by yourself with a bit of skill – a detailed procedure is available in the article Installation of a Sewer Check Valve Step by Step in this Knowledge Center.

Conclusion – Valve Maintenance as an Investment, Not a Burden

A sewer check valve is a cheap and inconspicuous part of the system, but it can protect you from damages worth thousands of euros. Investing 30 minutes twice a year for its inspection and cleaning is by far the cheapest insurance you can get for your home. With proper and regular maintenance, a modern plastic check valve can reliably serve for 20 years without the need for replacement.

If you are unsure about the type of valve you have installed or are considering replacing it with a new one, also read other articles in this Knowledge Center – for example, Intermediate vs. End Sewer Valve: What is the Difference and Where to Use Each, What Diameter DN Do I Need for a Sewer Check Valve?, or Common Check Valve Failures – Why the Valve Does Not Seal or Gets Stuck. A complete range of intermediate valves in standard sizes can be found in the category PE fittings, drainage, valves.

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