Professional guide: bleeding water pumps in heating and hydrophore installations

As the design team of a pump manufacturer, we help users and installers every day with issues such as venting the central heating pump, how bleed the central heating pump, as well as how to carry out pump bleeding process in hydrophore systems or heat pumps. Below you will find an expert discussion of when the pump must be vented, what they are symptoms of pump air lock i symptoms of air in the system, and what it looks like Instructions for bleeding the circulation pump step by step. Remember: safe bleeding of the pump and correct diagnosis is the basis to ensure proper operation of the pump, efficiency and long life pump life.

Why is there air in the system and what does it mean for work?

Air enters the installation for several reasons: "quick" filling, leaks on the suction side, loss of static pressure, dissolved gases released during temperature and pressure changes, as well as during servicing before start of the heating season. As a result air in the system loses flow efficiency, appears noisy pump operation, circulate in the installation air bubbles, and radiators and floor loops heat unevenly. In an extreme case air clogged pump and whole heating system they experience cavitation, which can accelerate pump damage and fittings.

Modern installation venting systems (automatic air vents, micro-bubble separators) support the process, but in practice pumps require bleeding also manual - especially after service work, modernization or a longer stop before heating season.

Quick diagnosis: when requires bleeding and what to check first?

• Noise / buzzing / knocking – a characteristic "squelching", metallic knocking or cyclical shuffling sound indicates bubbles in the rotor. It's classic symptoms of pump air lock.
• Uneven heating – some cold radiators in the upper parts; operation of the heating installation is disturbed.
• Performance drop – is decreasing circulation pump efficiency, heating time increases; falls heating system efficiency.
• Manometer and flow meters – jumps or lack of stabilization after starting the circulation pump.

If you see the above symptoms, bleeding must be carried out. Good a vented pump requires a short verification of parameters and tightness to confirm that venting system continues automatically.

Safety and preparation

Each safe bleeding of the pump requires basic measures: disconnecting the power supply, if the procedure requires it (some circulation pumps are vented during operation - check the instructions), eye and hand protection, protecting the workplace against hot water. Before you start perform bleeding of the pump, make sure that the static pressure and water level in the expansion vessel are as designed heating installation. For hydrophores: check the non-return valve and the tightness of the suction pipe - without it flooding the pump with water and restarting will be ineffective.

Central heating circulation pump – manual procedure by bleed screw

In many devices central heating circulation pump has a cork on the front bleed screw. The following steps of the bleeding process are standard on numerous models central heating pumps and are practical Instructions for bleeding the circulation pump:

1. Locate bleed screw on the front of the body (usually a slot for a flat screwdriver).
2. Depending on the model – the pump should operate at low speed or be disconnected. If the manufacturer allows bleeding "with the rotor running", this is possible quick pump bleeding.
3. Gently loosen the screw - you will hear the hiss of escaping air. When steady streams of water appear without bubbles, tighten the screw.
4. Check for leaks, top up the water in the system (if it is an open system/with an expansion vessel) and run the maximum speed for a few minutes - venting system the rest of the microbubbles.

Like this venting the installation is fast and effective, especially after short stops or service. Remember to the system should be bled also on radiators/floor loops (if there are manual air vents), because by itself circulation pump will not remove air embolisms in distant branches.

Automation and self-venting function

Many modern devices central heating circulation supports automatic air removal. After the first start, set the high gear for about 30 minutes and the air will escape through the vents in the boiler and distributors. This is a completely valid method bleeding the heating system and guarantee that pump properly vented will enter the nominal operating curve.

Table – pump bleeding operations and follow-up after the procedure

Bleed the circulation pump – when manually and when "systemically"?

If the installation has micro-bubble separators and automatic air vents, usually venting system in circulation. However, after major works (e.g. replacing the boiler) need to bleed the pump manually appears often. Then bleeding must be carried out pumps and at the same time venting the installation on manifolds and radiators. This approach gives pump effectively vented and equal temperatures throughout the facility.

Venting the heat pump and ground source circuits

In heat pumps (air-water, ground-water) bleeding the heat pump applies to both the heating circuit and - in the case of ground systems - brine. It is recommended to use a flushing station (high flow service pump) to bleed the pump and mains in continuous circulation mode with reversal. After initial flushing and bleeding, everyone worked for a short time circulation pump in maximum mode it allows you to remove microbubbles into the separator. Good practice is high-point air vents and a microbubble separator installed where the solubility of gases is the lowest (high temperature, low pressure), which accelerates bleeding the heating system.

Hydrophore pump – “venting” by flooding (priming)

Water hydrophore pump does not work properly if there is air in the suction line. That's why bleed the hydrophore pump by full flooding the pump with water and the suction pipe through a dedicated filling plug. In practice, this is crucial steps of the bleeding process in hydrophore systems:

1. Close the discharge valves, pour water into the body until no more fluid comes out air bubbles.
2. Make sure the non-return valve at the suction end is functional; A leaky valve is common need to bleed the pump “over and over.”
3. Start - if the suction does not "catch" the water column, add water and try again. Sometimes the pump is working several cycles until it reaches a stable water column.

This approach, although colloquially called "venting", is essentially priming - restoring a continuous column of liquid to operation of the hydrophore pump it's back to normal. Use it to be sure modern hydrophore pumps with dry-running protection and a flow sensor – you will reduce the risk pump damage.

Assembly tips

• Suction route as short and tight as possible; minimize kinks – it supports proper operation of the pump.
• A manual air vent at the highest point of the discharge line makes it easier venting the installation after service.
• Regular pump maintenance and checking the non-return valve will extend pump life.

Central heating – on-site practice

In season heating season and at start of the heating season we see the most questions about how bleed the circulation pump and how bleed the central heating pump in single-family houses. In short: central heating pumps we first bleed the air locally (cap), then linearly (manifold/radiators), and finally we start the automatic system installation venting systemsto complete the process. Well chosen circulation pump parameters (lifting height and resistance) is a guarantee that circulation pump operation will "pull" the remaining microbubbles through the separators.

Frequently asked questions and answers

How do I know that requires bleeding?

Noise, loss of comfort and deregulation of circulation are typical symptoms of air in the system. If after a short run at maximum speed and bleeding the radiators, you can still hear the noise, bleeding must be carried out pumps and sections. After the full treatment pump effectively vented works smoothly and quietly.

Is bleed the fuel system is this the same as venting the central heating?

No - this is a completely different procedure for powering oil boilers and engines. In central heating hydraulics we are talking about water/glycol solution. In this guide we only describe venting the installation water and how bleed the circulation pump and hydrophore pump.

Is regular bleeding of the pump is it necessary?

If the system is tight and has functional separators and automatic air vents, regular bleeding of the pump comes down to inspection after service and filling. However, always after greater interference in heating system the system should be bled.

What if central heating circulation pump does it have a self-venting mode?

Take advantage - it's fast and safe. After the start, set the maximum gear and run for several to several dozen minutes. That's a perfectly acceptable way to go bleeding the heating system. If in doubt – bleed the circulation pump additionally with a cork.

Checklist – before you start and after you finish

• Before: verify the filling pressure heating system, condition of air vents, access to the plug, occupational health and safety protection.
• During: drive safe bleeding of the pump, control temperature and leaks.
• After: execute checking pump operation (silence, flow, no vibration), rate circulation pump efficiency, correct the settings.

Good design and service practices

Use microbubble separators at the point of low gas solubility, install automatic air vents at the highest points, and in the case of hydrophore pumps - ensure the correct non-return valve, diameters and suction tightness. Thanks to this pump properly vented will maintain the curve, the pump is working quieter, a pump life is growing. If you have any suspicions cavitation revise circulation pump parameters and installation resistances.

Summary and quick cheat sheet

If you see symptoms of pump air lock, bleeding must be carried out from pumps, through radiators, to distributors. Central heating pumps and each central heating circulation pump should have access to the cork; some models allow bleeding during operation. In hydrophores "bleed the hydrophore pump” through total flooding the pump with water. Once done, execute checking pump operation. Only pump effectively vented and correctly selected use circulation pumps will provide comfort in central heating and reliable pump operation for years.

Our service teams emphasize that circulation pump in systems central heating is the heart of the circulation: correct venting, stable filling and proper automation are the conditions for this circulation pump and others central heating pumps they did not lose their efficiency. When circulation pump will be correctly diagnosed and vented, circulation pump works quietly, a heating system reaches the set parameters faster.

Attachment: glossary and most important terms

• Bleed screw – plug on the front of the pump for bleeding air.
• Microbubble separator – installation device that “catches” microbubbles and supports them venting the installation.
• Priming – full flooding of the body and suction in the hydrophore; yes bleed the hydrophore pump effectively.
• Self-venting – automatic function of many pumps; speeds up pump bleeding process.