Choosing Accessories by Pump Type – Circulation, Borehole, Sewage

Choosing accessories according to pump type – circulation, borehole, sewage

If you have ever wondered why one accessory works perfectly with a circulation pump in the boiler room, but is completely unsuitable for a sewage pump on a construction site – you are not alone. This is one of the most common confusing areas when purchasing and installing pumps. The reality is that different types of pumps have fundamentally different operating conditions, different mechanical and thermal requirements, and therefore completely different requirements for accessories. Choosing the wrong valves, couplings or fastening elements can mean leaks, reduced equipment lifespan, or in the worst case, a failure of the entire system.

In this article, we will take a detailed look at the three most common categories of pumps – circulation (circular), borehole (submersible well), and sewage – and for each of them we will explain what accessories are suitable, why, and what mistakes are most commonly made in practice when choosing them. If you are looking for a more general overview of what to pay attention to when choosing, we recommend the article How to choose the right accessories for a pump – what to pay attention to, where you will find the basic selection criteria.

Why the type of pump matters when choosing accessories

Each type of pump operates in a different environment, with a different medium and under different pressure and temperature conditions. This directly affects:

• Material of the accessories – stainless steel, brass, plastic, galvanized, cast iron
• Types of seals – EPDM, NBR, FKM (viton), teflon
• Diameters and thread standards – G, DN, metric threads
• Pressure classes – PN6, PN10, PN16, PN25
• Mounting and pipe guiding methods – fixed, flexible, clip-on
• Resistance to aggressive media – clean water vs. muddy puddles vs. aggressive ground water

A failure in any of these parameters is usually evident: it drips at the flanges, the pressure drops, vibrations loosen the connections, or corrosion eats away at the valves within one season. The topic of corrosion and its prevention is covered in a separate article How to prevent corrosion and damage to pump accessories in heating systems.

Circulation pumps – accessories for heating and cooling systems

Circulation (circular) pumps are the heart of every central heating system. You will find them in the boiler rooms of family homes, in apartment buildings, hotels, and industrial buildings. They work with a heat transfer liquid – most often water or a mixture of water and glycol antifreeze – at temperatures typically from 20 °C to 110 °C and at operating pressures from 0.5 to 10 bar.

Valves and fittings for circulation pumps

The basic set of accessories for every circulation pump should include shut-off valves (ball valves) on both sides of the pump, so that it can be replaced without draining the entire system. For modern pumps such as Grundfos Magna, Wilo Stratos, or DAB Evosta, it is common to install special detachable flanges with an integrated ball valve – so-called service flanges. This saves a huge amount of time during service interventions.

Pressure class of the fittings is a crucial parameter for circulation pumps. Most standard heating systems operate at pressures up to 3 bar, but a safe choice is fittings in the PN10 class, ideally PN16. Never use plastic fittings with glycol mixtures above 60 °C – glycol increases the aggressiveness of the medium and some plastic materials degrade over long-term contact with it.

Brass flanges and threaded connections are standard for circulation pumps. Lead-free brass CR is currently required for installations with drinking water, while classic brass OT58 is still fully acceptable for heating. It also depends on what medium is flowing through the system – some anti-corrosion additives react with zinc in galvanized materials and cause deposits.

Seals and sealing compounds for circulation pumps

Seals are a topic that is often underestimated with circulation pumps until they start leaking. For hot water and steam up to 110 °C, the most suitable material is EPDM (ethylene-propylene-diene rubber). EPDM has excellent resistance to hot water, steam, and glycol mixtures. NBR (nitrile rubber) is a cheaper alternative, but at temperatures above 80 °C and in contact with glycols, it quickly hardens and cracks – which is a recipe for a leak.

Teflon tape (PTFE) is used for threaded connections, but for larger diameters (DN32 and above), it should be combined with hemp or special pastes such as Loctite 577 or Henkel Tangit. Teflon tape alone is not sufficient for larger threads and will eventually start to leak – this is a common finding in service calls.

Suspension brackets and mounting accessories

Circulation pumps should be installed so that the rotor axis is always horizontal (terminal box up or to the side, never down). Brackets and suspension brackets must support not only the weight of the pump itself, but also the adjacent piping and fittings – for a DN32 copper pipe with water, this can be 8–12 kg per meter. Use galvanized or stainless steel brackets, never plain steel – condensation in the boiler room turns plain steel into rusted debris within 2–3 seasons.

Anti-vibration pads under the pump are an underestimated accessory. Even a well-balanced pump transfers micro-vibrations to the structure, which in a quiet house at night, residents perceive as a buzzing sound. A 5–10 mm rubber pad under the bracket eliminates this problem.

Well pumps – accessories for wells and deep boreholes

Well (submersible well) pumps are a special category. They operate fully submerged in a well or borehole, where they pump cold, clean groundwater (typically 8–14 °C). These are slender vertical machines with a diameter of 4" (101.6 mm), 6", or 8" depending on the borehole diameter, with a head from 20 to 200 meters of water column and power from 0.37 kW to several kW.

It is precisely here that the selection of accessories is the most critical – once the equipment is mounted, you can only retrieve it from a 60-meter well with significant effort, and if something fails, the repair is expensive and time-consuming.

Discharge pipe and fittings for well pumps

The discharge pipe of a well pump must be designed for the maximum operating pressure of the pump. At a head of 80 m, this is approximately 8 bar + dynamic shocks during startup – therefore, a pipe with at least PN10, ideally PN16, is used. Material options include:

• HDPE (high-density polyethylene) PN10/PN16 – the most common material, light, chemically resistant, joined by fusion couplings or mechanical quick couplings. Diameter usually 32, 40 or 50 mm depending on the pump power.
• Stainless steel pipe AISI 304 or 316 – for aggressive waters with higher chloride or sulfate content or for higher quality drinking water. More expensive, but more durable.
• Galvanized steel pipe – a historical material, nowadays it is being phased out due to internal corrosion and contamination of drinking water with zinc.

Ropes and clamps for lowering and lifting the pump

One of the most important, yet most often underestimated parts of the well pump accessories is the safety rope. A pump hanging in a 50–80 meter well weighs 5–25 kg depending on the power, and the weight of the water in the discharge pipe must also be added. If the pipe bursts or the coupling becomes loose, the pump will fall to the bottom – and retrieving it is then extremely complicated.

A stainless steel safety rope is therefore a standard requirement for any responsible installation. The rope is attached to the pump and runs up to the well cover, where it is secured using a suitable clamp. For this purpose, the stainless steel rope clamp is used – a simple, but critically important fitting that must be able to withstand the full weight of the pump in an emergency retrieval. When selecting a clamp, you must know the rope diameter (usually 4–6 mm for pumps up to 10 kg, 6–8 mm for heavier ones) and ensure that the clamp is made of certified stainless steel AISI 304 or 316 – not from chrome-plated steel, which rusts within two seasons in the humid environment of the well.

We often see this mistake in practice: the installer saves money on the clamp and uses a cheap galvanized one, which corrodes after 3 years in the well's humidity and breaks when trying to lift the pump. Result: pump at the bottom, complicated service intervention, costs 5–10× higher than the price of a proper stainless steel clamp.

For more information on proper pipe sealing and securing of pump pipes, read the article How to properly seal and secure pump pipes – rope clamps and couplings.

Check valves and protection for well pumps

Every well pump must have a check valve (non-return valve) installed or built-in at the discharge nozzle. Without it, every time the pump is turned off, the water column in the discharge pipe will flow back into the well – causing water hammer, pump wear, and in extreme cases, mechanical damage to the pump. Many modern well pumps (Grundfos SP, Franklin Electric, Pedrollo 4SR) have a built-in check valve directly in the body, but it is reasonable to install an additional one at the well cover.

Dry-run protection is another necessity. Either in the form of a float switch in the well or an electronic protection (pressure switch with delay). Without it, in the event of a drop in water level, the pump runs dry, which damages the mechanical seal in a few seconds and burns out the motor in a few minutes.

Pressure vessels and control units for drilling systems

The drilling pump is usually not connected directly to the water supply – between it and the house's piping, there must be a pressure tank (hydro-pneumatic unit) and a pressure switch (pressurestat). The pressure tank with a membrane dampens water hammer, ensures a minimum water volume in the system, and prevents short cycling, which is fatal for the pump motor.

The volume of the pressure tank depends on the pump's power and household needs. For a family house with a 1.5–3 kW pump and a pressure switch set to 2.5–4.5 bar, a 60–100 liter pressure tank is commonly used. Smaller tanks (8–24 l) are common only in installations with a frequency converter (inverter), where the pump speed is variable and short cycling is not an issue.

Septic pumps – accessories for sewage, construction and flood water

Septic pumps are probably the hardest working pumps in their category. They pump not only water but also suspensions with solid particles – mud, sludge, sewage, rainwater mixed with sand, construction waste. You encounter them on construction sites, in sewage pumping stations, in septic tanks, during floods, in cellars after water damage. They operate submerged, are exposed to mechanical wear, chemical effects and unpredictable operational loads.

Discharge hoses and rigid piping for septic pumps

Unlike drilling pumps, discharge hoses are often used instead of rigid piping for septic pumps. Hoses are flexible, easily movable and suitable for temporary installations. However, they must meet several parameters:

• Inner diameter: according to the pump's power, typically 25, 32, 50, 80 or 100 mm
• Pressure: at least PN6, for pumps with a discharge over 15 m we recommend PN10
• Material: PVC reinforced hose with reinforcement for clean water and light sludge; for more aggressive sewage or chemicals, rubber or neoprene hose
• Connection to the pump: hose clamp (stainless steel for permanent installations, galvanized for temporary) or Camlock quick coupling

Camlock couplings are standard in this segment for temporary use – they allow quick connection and disconnection of hoses without tools. For septic pumps, versions made of aluminum alloy are commonly used for light sludge and stainless steel for more aggressive sewage.

Float switches and protection for septic pumps

A float switch is for a septic pump what a thermostat is for heating – it controls the pump's switching on and off depending on the liquid level. There are two main variants for septic pumps:

• Integrated float – directly on the pump body (common in compact pumps up to 0.5 kW), simple, but does not allow setting switching levels
• External float on a rope – suspended separately from the pump, switching levels adjustable by rope length; suitable for larger sumps and pumping pits

The rope float is also where mistakes are often made when selecting accessories. The rope on which the float hangs must be made of stainless steel or polyamide – not plain steel. In a wet environment such as a septic tank or pumping pit, a metal rope without protection will rust in one year. Stainless steel rope clamp is especially useful here for securing the rope float or for fixing the discharge hose – a small accessory with a big impact on the reliability of the entire installation.

Materials of accessories for septic pumps – what lasts and what doesn't

For septic pumps, the accessories must withstand mechanical wear from solid particles, chemical effects of sewage and biological degradation. We most often encounter the following materials:

• Cast iron – for large valves and pits, resistant to wear, but prone to corrosion in aggressive sewage
• Polypropylene (PP) – for chemically aggressive environments, light, but lower mechanical resistance to abrasion
• Stainless steel AISI 304 or 316L – for demanding conditions, septic tank applications with aggressive sewage, maximum durability
• Galvanized steel – only for temporary installations and clean water; not recommended for sewage and sludge

Special accessories – what applies to all pump types

There are several types of accessories that are relevant across all three categories of pumps, and the differences here are more in the parameters than in the concept.

Connection threads and standards – DN vs. G vs. metric

One of the most common reasons for incorrect selection of accessories is the confusion of thread standards. The same thread standards apply to all types of pumps, but their typical use differs:

• G (BSP – British Standard Pipe) – pipe whitworth thread, the most widespread in European heating technology and in pumps. G1/2", G3/4", G1", G1¼", G1½" are the most common sizes for circulation pumps.
• DN (nominal diameter) – designation of the diameter of a flange or pipe, e.g. DN25 corresponds to G1". Used for flanged connections of submersible pumps and larger sewage pumps.
• NPT (National Pipe Thread) – American conical thread, rare in European practice, but appears in some imported pumps.

A detailed table of diameters and threads can be found in the article What diameter and type of connecting material do I need for my pump, which also includes conversion tables between standards.

Flexible connections and anti-vibration elements

Flexible hose couplings (vibrex couplings, rubber compensators) between the pump and the pipe are recommended for all types of pumps where there is a possibility of transferring vibrations to the pipe or structure. For circulation pumps, these are compensators made of EPDM rubber with fabric reinforcement in the PN16 class. For submersible pumps, they are used less often, since the pump is submerged. For sewage pumps installed in a fixed installation (pumping pit), rubber compensators on the discharge are standard.

Filters and coarse sieves

Before every circulation pump, a sludge filter (coarse sieve, Y-filter) with a mesh size of 0.5–1 mm should be installed. Mechanical impurities in the system are one of the main causes of premature wear of the pump's mechanical seal. For submersible pumps, special sand filters are installed on the well cover. For sewage pumps, the situation is reversed – here it is the macerators and coarse sieves directly in the pump body, which protect the system from larger pieces of solid waste.

The topic of common faults and water leaks is covered in the article Common faults and water leaks in pump accessories – causes and solutions, which also includes tips on how to distinguish a leak at the seal from a leak at the thread connection.

Practical scenarios from practice – how to make decisions

Scenario 1 – Replacement of a circulation pump in a family house: The customer replaced the old Grundfos UPS 25-60 circulation pump with a new Grundfos MAGNA1 25-60. The new pump has the same shaft distance of 180 mm and thread G1½". The customer assumed that the original flanges could be used – but the old flanges were brass with hardened and cracked NBR O-rings after 15 years. When installing the new pump on the old flanges, it started to leak immediately. The correct procedure: always replace the seals when replacing the pump, ideally also replace the flanges with new ones and fresh EPDM seals. Step-by-step installation of accessories is described in the article Step-by-step installation of accessories to a circulation pump.

Scenario 2 – Installation of a submersible pump for the garden: The customer had a new 55 m deep well and installed a Grundfos SP 3A-9 pump. The discharge pipe PE32 PN10 was in order. He forgot the safety rope – "after all, nothing will happen". After a year, the service technician checked the pump and during lifting, the pipe connection loosened. The pump caught on the wall of the well, but without the rope, it would have been at the bottom. Since then, the customer installs a rope with a stainless steel clamp as standard. Regular inspection and maintenance of accessories are described in the article Maintenance and inspection of pump accessories – how to extend their lifespan.

Scenario 3 – Sewage pump on a construction site: The construction company used a Grundfos Unilift CC 7 M1 sewage pump to pump water from a foundation pit. They used a 50 mm PVC hose with galvanized hose clamps. After 3 weeks in an aggressive underground environment, the clamps started to rust and loosen, and the hose burst at the joint. When replacing, they correctly used stainless steel clamps and a more durable rubber hose PN10 – no further problems during the entire construction period.

Most common mistakes when choosing accessories – summary

• Use of NBR seals at temperatures above 80 °C (instead of EPDM)
• Galvanized fittings in glycol mixtures or sewage
• Omitting the safety rope for submersible pumps
• Incorrect pressure class of accessories (PN6 where PN10/16 is needed)
• Mixing up thread standards G and NPT when importing pumps
• Missing check valve for submersible pumps
• Cheap plastic hose clamps for sewage pumps in an aggressive environment
• Undersized pressure tank (hydrofor) – short-cycling of submersible pumps

A detailed overview of what to look for during each inspection of accessories can be found in the article Common questions about accessories for heating and water pumps.

Frequently asked questions (FAQ)

Can I use the same flanges for different types of circulation pumps?

It depends on the thread diameter and shaft distance. If the new pump matches the thread (e.g. G1½") and shaft distance (e.g. 180 mm) of the old one, the flanges are geometrically compatible. Nevertheless, always replace the O-rings or flat gaskets – old seals become hard after years and will definitely start to leak after disassembly and reassembly. Never install a new pump on old seals.

What rope and clamp are suitable for a submersible pump at a depth of 60 meters and a weight of 8 kg?

For a pump of 8 kg at a depth of 60 m, we recommend a stainless steel AISI 316 rope with a minimum diameter of 4 mm, calculated with a safety factor of 5:1 (minimum rope load capacity of 400 kg). The clamp must be certified for the corresponding load – use a stainless steel rope clamp suitable for a diameter of 4–6 mm, ideally in duplicate (two clamps in a row). General rule: two days of solving the correct clamp selection saves days (and thousands of euros) in case of a failure at the bottom of the well.

Must a sewage pump always have a float switch?

Not necessarily – it depends on the application. If the pump is operated by someone physically present (e.g. pumping out a basement after flooding), it can run without a float switch under human supervision. For autonomous pumping (pumping pit, septic tank, accumulation pit), a float switch is absolutely necessary. Without it, the pump will run dry in an empty pit and the mechanical seal will burn out, followed by the motor – usually within 1–5 minutes. Dry-run protection costs a fraction of the pump's price.

Why is stainless steel accessories recommended instead of galvanized for submersible pumps?

In the environment of a well, the accessories are constantly exposed to moisture, condensation, and groundwater, which may contain chlorides, sulfates or other aggressive substances. Galvanized surface treatment typically lasts 2–5 years before corrosion starts in such conditions, while stainless steel AISI 304 and 316 lasts 20+ years. Moreover, corrosion of galvanized parts (including clamps and brackets) can contaminate drinking water with zinc ions. For all elements that are permanently submerged or in a humid environment, stainless steel is the only reasonable long-term choice. A detailed comparison can be found in the article Stainless steel vs. galvanized accessories for pumps – which is better.

Can I use a regular garden hose for the discharge of a sewage pump?

Using a garden hose for the discharge of a sewage pump is very common – and very bad – improvisation. Garden hoses are mostly dimensioned for PN4–PN6 and are intended for clean water. Sewage pumps typically achieve a discharge of 8–15 m (0.8–1.5 bar) and, in the case of sewage with solid particles, pressure surges during startup can temporarily reach double that. A garden hose is not sufficient for this and will burst. Always use a hose explicitly marked for pumping (suction/discharge hose, PN10), made of suitable material and with stainless steel hose clamps.

How can I tell that the accessories are incompatible with my pump before installation?

The most reliable method is to compare the pump's technical documentation (DN/G throat diameter, working pressure, maximum temperature, type of medium) with the technical parameters of the accessories. When purchasing accessories, check: 1) thread – it must match exactly (G or DN), 2) pressure – PN fittings ≥ maximum pump pressure, 3) temperature – the sealing material's temperature resistance must exceed the maximum medium temperature by 20–30 °C as a reserve, 4) material – compatible with the medium (glycol, flush water, clean water). If you are unsure, take a look at the article How to choose the right accessories for a pump – what to pay attention to, where these criteria are clearly listed.

Conclusion – key principles of accessory selection according to pump type

Selecting accessories for a pump is not only about fitting the correct thread. It is about understanding the entire operating environment – temperature, pressure, medium, long-term humidity, chemical stress. Circulation pumps require temperature-resistant brass or stainless steel fittings with EPDM seals; borehole pumps deserve stainless steel safety ropes with reliable stainless steel rope clamps and HDPE discharge pipe; sewage pumps require mechanically strong and chemically stable accessories adapted to the specific medium.

Every compromise in the accessories – a cheaper clamp, an unsuitable seal, an undersized hose – will later manifest as a failure, a leak, or in the worst case, the loss of the entire pump. An investment in the right accessories is also an investment in the reliability of the entire installation for years to come. The entire range of pump accessories can be found in our category, where you can filter by material, diameter, and pressure rating.

Do you have a question about this topic?

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