Installation of Check Valve and Angle Valve: Where and How to Install Them
Installation of check valve and angle valve: where and how to install them
The check valve and angle valve are among those plumbing components that most people take for granted – they are small, inexpensive, and at first glance inconspicuous. Despite this, they are parts without which many household water systems would simply not function properly, or would even be dangerous. In practice, we repeatedly encounter situations where incorrect installation of a check valve or angle valve is the cause of water leaks, backflow, appliance damage, or the need to completely shut off the water supply for every minor repair. This article will explain what these valves are, where exactly to install them, how to proceed with installation, and what to pay attention to in order to avoid the most common mistakes.
What is a check valve and how it works
A check valve (also known as a non-return valve or one-way valve) is a unidirectional shut-off device that allows water to flow only in one direction – in the direction of flow – and prevents it from flowing back. It operates on a simple principle: inside the body, there is a spring-loaded flap or ball that opens under the pressure of flowing water and closes when the pressure drops or when the water tries to flow in the opposite direction.
There are several construction types of check valves available on the market:
- Swing type (swing check) – the flap rotates around a hinge. Suitable for both horizontal and vertical pipes where water flows upward. Simple construction, low pressure loss.
- Ball type (ball check) – the ball seals the seat. Resistant to contamination, suitable even for water with coarser impurities.
- Spring type (spring check) – the flap is secured by a spring. Suitable even for vertical positions where water flows downward, more compact, faster closing.
- Diaphragm type – a rubber diaphragm replaces the flap. Used mainly in sanitary taps and appliances.
For domestic cold and hot water systems, spring or swing check valves with threaded connections (mostly ½" or ¾") are used in the vast majority of cases. Their pressure loss is typically 0.1–0.3 bar at normal flow, which is negligible in practice.
What is an angle valve and what it is used for
An angle valve (also known as a corner valve or angle stop valve) is a shut-off valve that connects the water supply in the wall to the flexible hose connection of a device – such as a tap, toilet cistern, dish rack, washing machine, or water heater. The name "angle valve" comes from its geometry: the inlet and outlet are perpendicular to each other, forming a 90° angle.
An angle valve performs two basic functions:
- Shutting off the water supply to a single device without having to close the main shut-off valve for the entire apartment or house.
- Regulating the flow – in most angle valves, it is possible to adjust the flow by turning the handle from fully closed to fully open.
An angle valve is not only a practical tool for plumbers. It is also a safety feature: if your tap starts dripping or water starts leaking from a flexible hose of a toilet, it is enough to close the angle valve in the cabinet under the sink and fix the problem without the entire household being without water.
Angle valves are typically made of brass (most common, durable, long-lasting), chrome-plated brass (more aesthetically pleasing for visible areas), and less commonly from stainless steel or plastic. Thread sizes for common household use are most often ½" (DN15) on the inlet and ½" or ¾" on the outlet. More about correctly reading thread sizes can be found in the article Pipe diameter and thread sizes: how to correctly read the marking ½", ¾", 1" in the Knowledge Center.
Where to install check valves: specific locations and reasons
Correct placement of a check valve is just as important as its quality. An incorrect position or a missing valve can cause serious problems – from contamination of drinking water due to backflow to failure of the pressure tank or water heater.
Before the water storage heater (boiler)
This is probably the most important location for installing a check valve in a household. Cold water enters the boiler through the lower connection. As the water heats up, it expands and the volume increases – without a check valve, this expanded water could flow back into the cold water supply and cause unpleasant pressure fluctuations, or even hot water could end up in the cold water supply. In addition, the check valve also protects the system in cases where the pressure in the network temporarily drops (e.g., during repairs on the public water supply).
Note: when you install a check valve before the boiler, the system becomes a closed loop. The volume of expanded water must go somewhere – therefore, it is essential to also install an expansion tank or to check that the boiler’s safety valve is functional and properly set. Without this, pressure could rise dangerously.
On the water supply to the washing machine and dishwasher
The European standard for connecting washing machines and dishwashers (EN 1717) requires protection of drinking water from back-siphonage. In practice, this means that a check valve must be installed on the supply of cold (and possibly hot) water to these appliances. Many modern washing machines and dishwashers have a check valve integrated directly into the supply hose, but if you are unsure, an external check valve is a cheap insurance with great value.
On the hot water circulation pipe
In apartment buildings and single-family homes with hot water circulation, a check valve is installed on the discharge of the circulation pump. It prevents the water from freely flowing back through the circulation loop when the pump is off. Without the valve, the hot water in the pipes would cool down on its own and cause heat losses.
Behind the pumping station or pump
Every pump – whether it is a well pump, garden pump, or transfer pump – should have a check valve on the discharge. The reason is simple: when the pump stops, without a check valve, the column of water in the pipe returns back and the pump loses its so-called “self-priming” effect. On the next start-up, the pump then has to prime again, which unnecessarily strains it and shortens its lifespan.
Behind the water meter (water gauge)
The network manager or water company sometimes requires the installation of a check valve directly behind the water meter. The reason is to protect the public water supply network from contamination from the internal distribution system of the consumer. In some countries, this is even a legal requirement.
On the garden water supply and irrigation
If you have a garden water supply with a submersible pump or a direct connection to the supply and you irrigate from an open container (e.g., a barrel with rainwater), a check valve prevents rainwater from flowing back into the drinking water supply. In gardening applications, this is a hygienically critical detail.
Where to install angle valves: specific locations and situations
Under the sink and basin
A classic location for an angle valve. Each water supply (cold and hot) to the sink faucet should have its own angle valve. When the faucet starts dripping or when you want to replace the flexible hose, it is enough to turn the valve and work without interrupting the water supply for the rest of the apartment. In practice, you will appreciate this especially in homes where the main shut-off is in the basement or technical room.
Under the toilet tank
An angle valve on the water supply to the toilet tank is an absolute necessity. Membranes and flappers wear out, and the tanks start to leak – and without an angle valve, every such repair would mean shutting off the entire water supply. A typical size is ½" on the inlet, with the outlet directly on the flexible hose to the tank.
To the washing machine, dishwasher, and refrigerator with an ice maker
An angle valve (or a straight shut-off valve) on the water supply to the washing machine and dishwasher is a given. With modern appliances that have a fill valve, the safe option of being able to shut off the supply without dismantling is key. Install the valve always in an accessible location – not behind the appliance, where you would not be able to reach it.
To the water heater (boiler) – on the cold and hot side
An angle valve on the cold water inlet to the boiler is essential: it allows you to disconnect the boiler from the supply during service work without turning off the water in the entire house. An angle valve on the hot water outlet from the boiler is also recommended – again for service accessibility.
On each connection to the sanitary fixture
Modern installation philosophy states: each fixture should have its own shut-off valve. A shower, bidet, urinal, automatic washing machine – wherever it connects to the water supply, there should be an angle or straight valve. This practice significantly simplifies maintenance and service.
Installation procedure for an angle valve: step by step
Installation of an angle valve is not technically complex, but it requires attention to detail. A poorly sealed connection under plaster or behind bathroom furniture may only become apparent after months – and the damage is often unpleasant. Here is a proven procedure:
Preparation and tools
- Adjustable wrench (pipe wrench) or valve wrench
- Teflon tape (PTFE tape) or hemp fiber with sealing paste
- Hose and bucket (for residual water)
- Flexible hose with the correct length and diameter, if needed
Step 1: Close the water supply and drain
Before any work, close the main shut-off valve for the respective circuit or for the entire apartment. Open the valve or outlet to allow residual water to drain and reduce pressure in the pipe. Never work on a pressurized pipe.
Step 2: Dismantle the old valve (if present)
If replacing an old angle valve, carefully remove it with a wrench. Be careful with the pipe in the wall – it can sometimes be rusted or brittle. If the old thread is damaged, it may be necessary to replace the pipe as well.
Step 3: Prepare the thread and seal
Clean the external thread on the pipe in the wall from the old sealing material. Wind Teflon tape around the thread in the direction of the thread (clockwise when looking at the end of the thread) – usually 5–8 layers for ½". If using hemp, apply sealing compound and wind the hemp evenly. The seal must cover the entire length of the thread, not just the first few turns.
Step 4: Screw in the angle valve
Mount the angle valve by hand and ensure the correct orientation of the outlet (towards the device). Then tighten with a wrench. Usually, tightening to the end + about 1–2 turns with the wrench is sufficient. Do not over-tighten – a cracked brass valve body is an unnecessary expense. The arrow on the valve body must match the direction of water flow.
Step 5: Connect the flexible hose
Connect the flexible hose (stainless steel braided, length as needed – commonly 30, 40 or 50 cm) to the outlet of the angle valve. Hoses have a threaded (internal) connection on both ends, so the sealing is ensured by a rubber O-ring inside – do not use Teflon here. Tightening by hand + one turn with a wrench is usually sufficient.
Step 6: Put into operation and check for leaks
Open the angle valve fully, then slowly open the main shut-off. Visually check all connections – is there any dripping? Tighten again if so. Let the system remain under pressure for at least 10–15 minutes and check again. Dry connections = good work.
Installation procedure for a check valve
The procedure is similar to that for an angle valve, but with a few important specifics:
Correct orientation – this is the basis
Each check valve has an arrow on its body indicating the direction of water flow. This arrow must point in the direction of normal water flow. A check valve installed in the opposite direction will not function at all – it will remain permanently closed or permanently open (depending on the type). Check the orientation twice before sealing and tightening.
Installation position for the flap type
Certain flap check valves (swing check) require horizontal installation – the flap opens and closes by gravity, and vertical installation (where water flows downward) may cause the flap to remain open due to its own weight. Spring-loaded types are indifferent to position and can be installed horizontally or vertically (for flow upwards or downwards).
Position in the water installation chain
A check valve is usually installed after the filter and before the device it protects. Recommended sequence of valves on the water supply to the house/apartment:
1. Main shut-off → 2. Filter (Y-filter or strainer filter) → 3. Pressure reducing valve (if needed) → 4. Check valve → 5. Branches to devices.
Regarding filters: if you are looking for a quality filter for your installation, consider for example Y-strainer filter, brass with stainless steel screen 2" or for larger branches Y-strainer filter, brass with stainless steel screen 4". A stainless steel screen is significantly more durable than a plastic one and is easier to clean. Learn more about choosing a filter in the article Water filters: Y-filter, angle filter or filter with reduction – which to choose.
Sealing and installation
The procedure for sealing and tightening is the same as for an angle valve – Teflon tape on the thread, correct tightening torque, and leak check after opening the supply. Check valves have a larger body than angle valves, so they may be slightly more prone to cracking under over-tightening – follow the recommended torque.
What to do if water pressure is too high – connection to pressure reducing valve
It is very common that a customer installs a check valve and angle valves, but forgets about pressure regulation. If the pressure in the network is higher than 4–5 bar (which is common in many cities), you may encounter the following:
- Wear of seals on angle valves and taps much faster than normal
- Noise in the pipes (hammering, whistling)
- Increased water consumption
- Malfunctions of washing machines and dishwashers (their solenoid valves are usually dimensioned for max. 6–8 bar)
In such a case, the ideal solution is the installation of a pressure reducing valve. For example, pressure reducing valve ½" with manometer 0–10 bar is a compact solution for smaller households – thanks to the integrated manometer, you can easily set and monitor the working pressure. For larger houses or apartment buildings with multiple outlets, pressure reducing valve 1¼" with separate replaceable cartridge is suitable, where you can replace only the cartridge during service without dismantling the entire valve.
The recommended working pressure in the household distribution is 2.5–3.5 bar. Learn more in the articles What water pressure is correct in a household and how to set it and Installation of a pressure reducing valve: step by step.
Common installation errors – from practice
After years of field work, we keep seeing the same problems. Here are the most common ones to help you avoid them:
Incorrect orientation of the check valve
Installing a check valve "backwards" (against the flow direction) is by far the most common mistake. Result: no water, although the valve appears to be installed correctly. Always check the arrow on the valve body before sealing the thread.
Insufficient or excessive thread sealing
Too little Teflon = a leaking connection. Too much Teflon = the valve cannot be adjusted to the correct position, or the thread is damaged when tightened. The correct amount is 5–8 Teflon tape layers for a ½" thread, 8–12 for ¾".
Elbow valve installed in the wrong place or with incorrect outlet direction
Sometimes an elbow valve is installed so that the outlet points directly into the wall or to the device at a sharp angle – the flexible hose then works under tension and is more likely to burst. The outlet should point comfortably toward the device, without forcing it.
Missing expansion tank before the check valve on the cold water supply to the water heater
As we mentioned – a closed system without an expansion tank is potentially dangerous. The water heater's safety valve should not be used as the primary expansion protection – it is a safety measure, not a regular control element.
Use of unsuitable flexible hoses
Plastic-lined hoses (without stainless steel braiding) are suitable only for cold water and low pressure. For hot water and any pressure above 3 bar, always use stainless steel braided hoses with appropriate temperature resistance.
Installation of an elbow valve with a closed filter without prior cleaning of the filter screen
If you have a filter in your installation and you are working on the valves, don't forget to check and possibly clean the filter screen after completing the work – debris released during the work will settle there. More about the cleaning procedure can be found in the article Cleaning and replacing the filter screen: how to do it and how often.
Materials, dimensions and selection: a practical overview
When choosing an elbow valve or a check valve, several parameters are key:
| Parameter | Elbow valve | Check valve |
|---|---|---|
| Common sizes (DN) | ½" (DN15), ¾" (DN20) | ½", ¾", 1", 1¼" |
| Body material | Brass (Ms 58), chrome brass | Brass, cast iron, stainless steel, plastic |
| Maximum working pressure | 10–16 bar | 10–16 bar (common types) |
| Maximum temperature | +90 °C (brass with EPDM) | +90 °C (depends on sealing) |
| Sealing | EPDM, NBR, Teflon | EPDM, NBR, Teflon, rubber |
| Typical pressure loss | 0.05–0.2 bar at full opening | 0.1–0.3 bar at nominal flow |
For potable water systems, always choose valves certified for drinking water (marked with W or WRAS, EN 1213). Cheap valves without certification may release lead or other harmful substances into the water, which is unacceptable in potable water systems.
Maintenance, service and lifespan
Modern elbow valves are practically maintenance-free, provided you turn them slightly at least once a year. Valves that remain in one position (either open or closed) for years can become "stuck" – the stem may rust or fuse, and they won't function properly in an emergency. A simple preventive movement once a year is all you need.
Check valves do not require regular maintenance, but we recommend a visual inspection during every major system inspection (every 2–3 years). Signs of a faulty check valve: the water level in the water heater "fluctuates" without reason, you hear hammering after closing a valve, or hot water enters the cold water supply. In such cases, the simplest solution is to replace the entire valve – repair is not economically viable.
The lifespan of high-quality brass elbow valves and check valves, under proper pressure and water filtration, is 15–25 years. Water purity plays a key role here – impurities and deposits accelerate the wear of seals and moving parts. Therefore, a filter before the valves is not a luxury, but an investment in the longer life of the entire installation.
Frequently asked questions (FAQ)
Do I need to use a professional plumber to install an elbow valve, or can I do it myself?
Installing an elbow valve is technically simple and can be done by a skilled DIY enthusiast without plumbing experience. The conditions are proper thread sealing, observing the flow direction, and performing a pressure test after installation. If you are replacing an elbow valve with a new one without any changes to the piping, a professional is not a legal requirement. However, if you are installing a new system, renovating, or working on pressure systems in apartment buildings, we recommend consulting a plumber.
Can I install a check valve vertically (water flowing upward)?
Yes, but it depends on the type of valve. Spring-loaded check valves are universal and function properly in both horizontal and vertical positions (flow upward or downward). Swing-type check valves are primarily intended for horizontal piping or vertical piping with upward flow – downward flow may not allow the valve to close properly by its own weight. Always read the technical specifications of the specific product.
Why is the safety valve dripping after installing a check valve before the water heater?
This is a very common occurrence and directly relates to what we mentioned in the article: the check valve created a closed system. Water expands when heated (temperature from 15 °C to 60 °C means a volume increase of about 1.7 %), but has nowhere to escape. The water heater's safety valve (usually set to 6–8 bar) will start to drip, which is technically correct, but not a desirable long-term solution. Correct solution: install an expansion tank on the cold water supply before the water heater (volume 8–12 liters for a standard 80–100 liter water heater).
What is the difference between an elbow valve and a straight (linear) valve?
An elbow valve has an inlet and an outlet at a right angle (90°), which is used for wall connections directly to a device placed next to the wall. A straight valve has an inlet and an outlet in the same axis – it is used where the piping runs parallel to the device, for example, for floor connections or long straight sections. Functionally, they are equivalent; the shape is chosen according to the installation geometry.
Can I use the same check valve for cold and hot water?
Most common brass check valves with EPDM sealing are certified for temperatures up to +90 °C, so they can be used for both cold and hot water. It is important to check the maximum temperature in the technical specifications – valves with NBR sealing are suitable only up to +60 °C. For check valves in hot water circulation or directly at the water heater outlet, always choose a version suitable for hot water and high pressure.
What to do if a corner valve leaks around the stem after years of operation?
A small leak around the stem (not through the body, but along the stem axis) is usually caused by wear of the sealing kit (O-rings or graphite seal). Some valves allow the seal to be replaced without dismantling the entire valve – it is enough to close the supply, unscrew the top nut, replace the O-ring and reassemble. If the valve is not serviceable (older type), it is simpler and cheaper to replace it with a new one.
Conclusion: small fittings, big difference
Check valves and corner valves are inconspicuous, yet truly important components of every reliable household plumbing system. Correct placement of the check valve before the water heater, after the pump and on the supply to appliances significantly extends the lifespan of the equipment and protects the hygiene of drinking water. A corner valve at each appliance, in turn, provides daily freedom during maintenance and repairs – without turning off the entire house, without stress, without flooded floors.
Investing in quality fittings pays off many times over: fewer faults, simpler servicing, longer appliance lifespan. And if you are unsure about the correct pressure in the network or you are interested in a comprehensive solution from a filter through a pressure-reducing valve to a check valve, further information can be found in other articles in our Knowledge Center – for example in Common questions about plumbing fittings or in Common faults of pressure-reducing valves and filters: causes and solutions.
Do you have a question about this topic?
Having trouble deciding or dealing with a specific situation in your household? Write to us – we are happy to help.