How to choose the right pump accessories – what to pay attention to

We are still preparing products.

But you can look at other categories.

Why the choice of accessories is just as important as the choice of the pump itself

Many people carefully choose a pump – comparing performance, flow rates, manufacturers, and warranties – but then reach for the first or cheapest accessory they find. This decision often comes back to haunt them, sometimes in a very costly way: in the form of a pump pulled from the bottom of a well with a broken rope, or flooded basements due to an unsuitable hose coupling that couldn't withstand the pressure. Over the years of practice, I have seen dozens of such cases, and most of them had one thing in common – the underestimation of accessories.

Pump accessories are not just a random collection of small items. They form a system of components that ensure safe installation, reliable operation, and a long service life of the entire pumping system. These include various types of clamps, couplings, suspension systems, check valves, vibration dampers, pressure gauges, hoses, flanges, and other mounting materials. Each of these elements has its specific requirements, and the wrong choice can shorten the life of the entire device or even cause a failure.

This article will guide you through the complete topic of selecting accessories – from basic classification by function, through material parameters, dimensions and pressure classes, to practical scenarios from the field, where you can verify whether you have made the right choice.

Basic categories of accessories and their function in the system

Before we get into the details of selection, it is important to understand what groups the accessories consist of. Each group performs a different role, and a mistake in any of them can cause problems of a different nature.

Mechanical fastening elements – clamps, couplings, suspension systems

This group includes everything that physically holds the pump in place or connects individual parts of the piping and hoses. A well-known example is rope clamps for submersible pumps – without them, it is not possible to safely lower and raise the pump from the well. Similarly, hose clamps, flanges, reducers, and various types of brackets belong here.

The basic criterion for selection is the material (more on that below), size (it must fit the specific diameter of the rope or hose), and load capacity. Load capacity is the most commonly underestimated parameter – people buy a clamp that holds 50 kg, but forget that the pump itself weighs 15 kg, the filled hose 8 kg, and any mud coating adds more kilograms. More about dimensioning load capacity can be found in the topic What diameter and load capacity does a rope clamp need for your pump.

Pressure and flow control valves

Check valves, safety valves, shut-off valves, membrane tanks, and pressure gauges. These elements regulate the direction of flow, pressure, and protect the system from water hammer. A check valve on the discharge side of the pump is mandatory in many installations (for example, in submersible pumps in wells) – without it, when the pump is turned off, the water returns back into the well, and the pump must create the entire pressure column from zero with every start, which dramatically shortens the motor's lifespan.

Damping and protective elements

Vibration dampers, flexible hoses, compensators. Pumps – especially powerful ones – generate vibrations during operation, which can spread through the piping, the building, or the well structure. Long-term vibrations fatigue connections, loosen screws, and can crack brittle piping. Rubber vibration dampers and flexible compensators are inconspicuous but extremely important components.

Electrical accessories and pump protection

This includes float switches, pressure switches, protective relays, control units, and cabling suitable for wet environments. Here too, it is true that "something I can connect" and "the right component" are two different things. A float switch with an unsuitable range can cause the pump to run dry, which can destroy mechanical seals and bearings.

Material of the accessories – the most important choice to make first

Material is probably the most important parameter that determines whether the accessory will last one year or twenty. In practice, we mainly encounter the following materials:

Stainless steel (AISI 304, AISI 316)

Stainless steel is the gold standard for most applications in contact with water and humid environments. Type AISI 304 is a common food-grade stainless steel suitable for fresh water, normal humidity, and outdoor environments. Type AISI 316 contains molybdenum, which gives it resistance to chlorides – it is suitable for seawater, swimming pool installations, and more aggressive chemical environments.

An example of a high-quality stainless steel component for pump suspension systems is, for instance, a stainless steel rope clamp, used to secure the suspension rope of a submersible pump in a well. A stainless steel version is important because the clamp is permanently submerged or at least exposed to the humid environment of the well, where a galvanized material would start to corrode within a few years.

Galvanized steel

Galvanized steel is a cheaper alternative suitable for environments with lower humidity or where the accessory is accessible and regularly replaced. In installations of submersible pumps in wells, galvanized accessories are not recommended – the zinc layer dissolves in contact with water (especially soft or acidic water), and corrosion of the base material begins underneath. A comparison of the service life of stainless steel and galvanized components is discussed in detail in the topic Stainless steel vs. galvanized clamps and couplings – which last longer.

Brass

Brass is mainly used for valves – valves, taps, reducers. It is resistant to corrosion in contact with water, easy to machine, and provides good sealing. It is not suitable for environments with aggressive chemicals or very soft (deionized) water, which can cause dezincification of the brass.

Plastic (PP, PE, PVC, PA)

Plastic components are light, chemically resistant, and affordable. They are suitable for low pressures and temperatures. The main disadvantage is mechanical brittleness at low temperatures and sensitivity to UV radiation (unless specially stabilized). Plastic hose clamps or distributors are fully sufficient for irrigation systems, but do not use them for pressurized water supply systems or for suspension applications with pumps.

Dimensions and compatibility – the most common source of problems in practice

Material is important, but dimensional compatibility is what determines whether the accessory can be installed at all. This is an area where the most mistakes are made in practice, even by experienced plumbers.

Threaded connections – BSP, NPT and metric threads

In European practice, we most often encounter the BSP thread (British Standard Pipe), known here as the G-thread or Whitworth thread. Common sizes are G 1/2", G 3/4", G 1", G 1 1/4", G 1 1/2", G 2". American pumps may have an NPT thread (National Pipe Thread), which is geometrically different – NPT is conical and BSP is cylindrical. These threads are NOT interchangeable, even if the pitch may be similar. Attempting to connect them leads to water leakage or thread damage.

In practice: when you buy a reducer or valve for a European pump – it is most likely that you need a BSP thread. When you buy an accessory for an American pump or a cheap Asian product sold on the American market – check the thread type in the technical specifications.

Flanged connections – PN and DN

For larger pumps (circulation, submersible, fire protection), flanged connections are used. Here, two values are key: DN (nominal diameter in mm) and PN (nominal pressure in bars). Flanges must have the same DN and PN, otherwise they will not fit – either physically (different bolt circle dimensions and hole diameters) or from the perspective of pressure class. Common PN classes are PN 6, PN 10, PN 16, PN 25. For domestic water supply systems, PN 10 is sufficient, while for industrial or fire protection systems, PN 16 or higher is required.

Cable diameter and clamps – what customers ask about most often

For suspended submersible pump systems, the cable diameter is crucial. The cable is selected based on the pump weight and well depth, and the cable clamp must fit the exact diameter of this cable. Common cable diameters are 4 mm, 5 mm, 6 mm, 8 mm, 10 mm. Stainless steel cable clamps must specify the range of diameters for which they are suitable – never buy a clamp without verifying that it matches the diameter of your cable.

Let me remind you that the load capacity of one clamp is not sufficient for the entire load – in practice, at least one clamp is always installed as the primary and another as a backup. Detailed dimensioning is discussed in the topic What cable diameter and load capacity does the clamp need for your pump.

Pressure classes of accessories – numbers that must match

Each component in a pressure system must be dimensioned at least to the maximum operating pressure of the system, ideally with a safety margin. In domestic water supply pumps, we typically operate at pressures of 3–6 bar. For a household, accessories with PN 10 (maximum pressure 10 bar) are fully sufficient.

Problems arise with terminal or safety accessories – a check valve or safety valve must be able to withstand not only the operating pressure, but also a possible water hammer (hydraulic shock), which can reach several times the operating pressure when a valve is closed quickly. Therefore, it is always recommended to use at least PN 16 check valves in systems with normal operating pressures of 4–5 bar.

For submersible pumps in deep wells, you must also consider the hydrostatic pressure of the water column above the pump. Every 10 meters of water depth corresponds to 1 bar of pressure. A pump in an 80-meter well therefore operates with an inlet pressure of up to 8 bar, which places increased demands on the accessories on the suction pipe as well.

Choosing Accessories According to Pump Type – Submersible, Surface, Circulating

The type of pump determines what accessories you will need. What works for a circulating pump in a boiler room is completely irrelevant for a submersible pump in a well. A detailed guide to selection according to types can be found in the topic Choosing Accessories According to Pump Type – Submersible, Surface or Circulating, but here we will go through the most important differences.

Submersible Pumps

Submersible pumps are fully immersed in liquid, which places the highest demands on the resistance of accessories to corrosion. You will need:

Suspension system – rope (stainless steel or polypropylene), stainless steel rope clamp for attachment to the edge of the well or to the discharge pipe, or alternatively a carabiner or hook
Check valve – inserted into the discharge pipe to prevent water from flowing back when the pump is turned off
Discharge hose or pipe – in stainless steel, PE or HDPE versions, with water couplings or threaded flanges
Float switch or dry run protection – to prevent the pump from running when the well is empty
Electrical cable with protection for wet environments – at least IP 68 for submersible applications

Surface Self-Priming Pumps

These pumps are installed above the water level and draw water from a well, tank or stream via a suction pipe. The accessories here include:

Check valve with a filter on the suction inlet – placed at the water depth, prevents the suction pipe from emptying and protects the pump from coarse impurities
Suction filter – a basket or strainer that captures mechanical impurities
Membrane pressure tank – dampens pressure fluctuations and extends the pump's lifespan by reducing the number of starts
Pressure switch – automatically starts and stops the pump according to the pressure in the system
Vibration dampers – rubber pads or flexible compensators on the inlet and outlet pipes

Circulating Pumps (Circulators)

Circulating pumps in central heating or hot water systems have a specific group of accessories:

Closing valves – ball valves or shut-off valves on both sides of the pump, so the pump can be replaced without draining the entire system
Impurity filters (strainer) – capture rust, seal fragments and other impurities from the installation that could damage the pump rotor
Air vent valve – at the highest point of the circuit
Pressure gauge – for monitoring operating pressure
Balancing valves – in multi-circuit systems for hydraulic balancing

Practical Scenarios from the Field – Where People Make Mistakes

After years in the field of heating and plumbing technology, I have identified several typical scenarios where accessory selection fails. Each of them represents a real case.

Scenario 1: Galvanized clamp in the well. A customer bought a submersible pump and a galvanized rope clamp because it was one-third cheaper than a stainless steel one. After three years, he tried to pull the pump out for service. The clamp was so rusted that it could not be opened with a key – it had to be cut. That would have still been okay. Worse was that the rope was damaged by corrosion at the clamp and when pulling (the old clamp was on top, the replacement underneath) it broke. The pump remained at the bottom of the well and its retrieval cost more than a new one. Prevention: always use stainless steel clamps.

Scenario 2: Missing check valve. A customer installed a surface pump without a check valve on the suction pipe (he thought he didn't need it because the pump had an internal one). The pump worked, but every morning at the first start, it had to be "primed" – water had to be manually poured into the suction part. In practice, he did this by loosening the shut-off and pouring in water. After a year, this became a routine ritual, until the pump burned out the motor due to insufficient water in the suction chamber. Result: pump replacement. Cost of a check valve: 8 €.

Scenario 3: Wrong size of strainer. During a heating system renovation, a new circulating pump was installed, but the strainer (impurity filter) had a DN 20 diameter instead of the required DN 25. The pump worked, but a throttling point was created, increasing resistance in the system, the pump operated with a lower flow and the radiators in the last row were cold. The problem was only discovered during an energy audit – a strainer for 12 € caused annual excess energy costs of several dozen euros.

Scenario 4: Pressure switch with incorrect setting. A customer bought a membrane tank and a pressure switch for a home water supply, but the switch was factory-set to 2.5/4.5 bar and the customer did not adjust it according to the tank size. Result: the pump turned on and off every 20–30 seconds (so-called "chattering"), which quickly wore out the motor and the switch contacts. After half a year, the pump burned out.

Compatibility with a Specific Pump Manufacturer

This is an area where customers often rely on "it will fit". In practice, it is not always the case. Some pump manufacturers (e.g. Grundfos, Wilo, DAB) have their own flange dimensions for circulating pumps, which are not always consistent with the standard DIN norm. Buying standard flanges and finding out that they do not fit the pump is a classic situation.

I recommend always:

Download the technical documentation for the pump and verify the actual flange dimensions (bolt hole spacing, hole diameter, flange thickness)
When purchasing accessories, provide the seller with the pump type and model, not just nominal dimensions
Always prefer original parts or verified alternatives from a reputable distributor for service parts (gaskets, ball bearings, O-rings)

Temperature and chemical environment – parameters that are often forgotten

When it comes to accessories for heating systems or industrial pumps, the temperature of the liquid is another critical parameter. Common rubber gaskets (EPDM) are suitable up to about 100 °C and for cooling/heating with water. For hot oils or aggressive liquids, gaskets made of NBR, FKM (Viton), or PTFE are required. Plastic components designed for cold water can deform and leak at temperatures above 60 °C.

Regarding chemical resistance: if you are pumping liquids other than clean water (muddy water, chlorinated pool water, garden fertilizer, weak acids), always verify the chemical resistance of all components. Manufacturers of accessories usually provide chemical resistance tables for their products. Ignoring this step can lead to rapid degradation of gaskets and couplings.

Installation and assembly – accessories are not enough to buy, they must be installed correctly

Even if you buy perfect accessories, incorrect installation can cause the same problems as a poor choice. The most common installation errors include:

Over-tightened threads – with threaded connections, it is easy to strip the thread when over-tightened, especially on plastic bodies
Missing or misaligned gaskets – O-rings must be properly placed in the groove; if they fall out or are misaligned, the connection will leak
Incorrect mounting direction of check valve – a check valve is unidirectional and has an arrow indicating the flow direction; if reversed, it will not function
Cable clamps mounted backwards – cable clamps have a specified tightening direction; reverse installation can reduce strength by up to 50 %

A detailed installation procedure can be found in the topic Step-by-step installation of pump accessories – a guide for DIY enthusiasts, and common mistakes are discussed in the topic Common installation mistakes for pump accessories and how to avoid them.

Maintenance of accessories – often ignored, yet crucial

Accessories not only require the right choice, but also regular inspection. Filters get clogged, gaskets age, anti-corrosion surfaces can be damaged, and screws can loosen. The recommended frequency of inspections depends on the environment and the intensity of operation:

Strainers and filters – cleaning at least once a year, more frequently in turbid water
Cable clamps and suspension elements – visual inspection each time the pump is removed (minimum once every 2–3 years), tactile inspection for corrosion and mechanical damage
Gaskets and O-rings – replacement with new ones at any disassembly (gaskets are cheap, reusing an old O-ring is usually not sufficient)
Membrane tanks – check the nitrogen pressure in the tank every year (standard value 1.5–2 bar, depending on the pressure switch setting)

More information on what and how to inspect can be found in the topic Maintenance and inspection of pump accessories – what and how often to inspect. Issues with corrosion and mechanical damage are discussed in detail in the topic Corrosion and mechanical damage of accessories – causes, prevention, and solutions.

Where to buy accessories and what to avoid when purchasing

Pump accessories can be found in online shops, hardware stores, and specialized heating stores. A few practical tips:

Do not buy "no-name" accessories without material markings – if the product does not indicate what it is made of (stainless steel, brass, EPDM...), it is usually not a good sign
Verify certifications for potable water – if the pump supplies drinking water, all components in contact with water must have a certification for contact with drinking water (in the EU, for example, WRAS, ACS, or the manufacturer declares compliance with the relevant standard)
Check the availability of spare parts – with less common manufacturers, it may be difficult to obtain replacement gaskets or membranes in five years
Do not combine different materials without considering galvanic corrosion – contact between stainless steel and zinc in a wet environment accelerates the corrosion of the zinc part

Most frequently asked questions (FAQ)

Do I need to buy a special cable for a submersible pump, or is a regular cable from the hardware store enough?

No, a regular steel cable from the hardware store is usually not sufficient. You need a cable made of stainless steel (AISI 316 or at least AISI 304), or made of plastic (PP, polyester), which is resistant to long-term submersion in water. A regular steel cable will start to corrode and weaken within one to two years. In addition to the material, also verify the cable's load capacity – it must be at least 3–5 times the weight of the pump (dynamic load during lifting can be significantly higher than static load). A properly dimensioned stainless steel cable clamp is always required with the cable.

What kind of check valve do I need for a submersible pump in a well?

For submersible pumps in wells, either a check valve with an external thread inserted directly into the pump's discharge port is used, or a check valve built into the well cover. The size (DN) must match the size of the pump's discharge port – most commonly G 1" or G 1 1/4". The material should be brass or stainless steel, since the valve is permanently submerged. Pressure class at least PN 10, for greater safety PN 16.

Can I use the same accessories for a heating and a water supply system?

Not always. Some components are universal (for example, brass ball valves), but others are specific. Gaskets for hot water in heating must withstand temperatures above 90 °C, while gaskets for cold water installations are not designed for that. Filters for water supply must have certification for potable water, which heating filters do not have. Membrane tanks for heating use different membranes (resistant to temperature and expansion of liquid when heated) than tanks for water supply. Always read the technical data sheet of the specific component.

How many cable clamps do I need for one pump?

At least two. The primary clamp is placed at the top (at the well opening or on the pipe rack) and carries the full load of the pump. The second clamp serves as a safety – it is placed lower on the cable and will catch the pump in case the primary clamp loosens or the cable breaks above it. In deep wells or with heavier pumps (over 20 kg), three clamps are recommended. Each clamp must have its own load capacity at least equal to the total load.

Do I need a strainer before a circulation pump if the installation is new?

Yes, especially. New installations contain chips, weld splatter, leftover flux, and fragments of gaskets and other dirt from construction. These impurities travel directly to the pump during the first start-up and can damage the rotor (circulation pumps have a very small clearance between the rotor and stator – 0.1–0.3 mm). A strainer before the pump is a life-saver. Clean it after the first heating season – you will be surprised how much dirt it catches.

What is the difference between a hose clamp and a cable clamp?

A hose clamp (or hose coupling) is used to secure a hose to a fitting – it compresses the hose end around the metal tip of the fitting and prevents water leakage. A cable clamp is a completely different component – it is a connecting element that joins two parts of a cable or serves as a stop on the cable. Both elements have their precisely defined functions and cannot replace each other.

Conclusion – the right choice of accessories is an investment, not an expense

Accessories for pumps make up only a small part of the total installation costs, but their poor selection can multiply the cost of the entire project several times. Properly dimensioned, made from suitable materials, correctly installed, and regularly checked accessories ensure that your pump will operate reliably for decades without unplanned outages or repairs.

When selecting accessories, follow a simple rule: type of pump → dimensions → pressure and load capacity → material → manufacturer compatibility. This approach will cover 90% of situations without major problems. The remaining 10% are specific cases (aggressive media, extreme temperatures, great depths), where it pays off to consult a specialist – this will help you avoid much higher costs later on.

If you are dealing with a specific situation involving a submersible pump and are unsure how to design the suspension system, take a look at the topic How to properly secure a pump in a well using a rope clamp and suspension system. For answers to specific questions from practical experience, there is also the topic Common questions about pump accessories – answers to what people most often deal with.

Do you have a question about this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.