what diameter and type of connection to choose for a 63 mm pressure gauge

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Selecting the correct pressure gauge for a heating system often focuses only on the measurement range, but a key factor for functionality and long service life is the correct type of connection and its diameter. An incorrect choice can lead to the need to use expensive reducers, which increase the risk of leakage or disrupt the accuracy of pressure measurement in the system.

Difference between axial and radial connections

When selecting a 63 mm pressure gauge, you first have to decide between two basic designs: axial (with a rear connection) and radial (with a bottom connection). Axial pressure gauges have a threaded connection located on the back of the device, which allows for direct mounting on the wall or into a distribution panel without the need to make bends in the piping. This configuration is ideal for space-restricted areas, where a radial pressure gauge with a bottom connection would hit an obstacle.

Conversely, radial pressure gauges have a connection oriented perpendicular to the face of the device, which requires a direct pipe input from below. This type is common when mounting on boiler bodies, where it is necessary to maintain a direct pipe axis without bends. For system solutions where clarity and easy replacement are important, we recommend the axial pressure gauge 0 - 10 bar, 63 mm, which is mounted directly into the panel without complicated connections.

Standard connection sizes G 1/8 and G 1/4

The most common standard for pressure gauges with a 63 mm dial diameter is the internal thread G 1/8 inch (approx. 9.7 mm), which is designed for typical domestic heating systems and smaller industrial applications. This diameter ensures sufficient flow of liquid into the manometric chamber without being sensitive to pressure shocks, which is critical during dynamic changes in the system. However, if you are working with larger industrial boilers or high-pressure systems, you may encounter the variant G 1/4 inch (approx. 13.2 mm), which provides higher mechanical strength and resistance to vibrations.

G 1/8 is the standard for most apartment and family homes.
G 1/4 is used in cases of strong vibrations or higher temperatures.
Checking the thread roughness is necessary before installing a new device.
An incorrect thread leads to the unnecessary use of reducers, which reduces reliability.
The G 1/8 thread is compatible with most standard heating valves.

Direct and indirect connection in practice

The technical implementation of the connection depends on the type of installation; it may involve either drilling directly into the pipe or using a tee (three-way valve) to isolate the pressure gauge. When using a tee, it is important that the internal hole of the tee is the same diameter as the pressure gauge connection to prevent the formation of dead zones where dirt can settle and affect measurement accuracy. Direct connection often uses pressure gauges with an axial connection, which allow for tight mounting on a flat surface, thus eliminating the risk of leakage due to better distribution of tightening force.

In practice, we have encountered cases where an incorrectly dimensioned tee caused blockage of the pressure wave channel, resulting in the pressure gauge showing zero pressure even when the system was fully operational. Therefore, when selecting a pressure gauge, for example, the axial pressure gauge 0 - 4 bar, 63 mm, it is always necessary to verify that the product datasheet states compatibility with standard tee systems. Choosing the correct connection means you can use standard T-pieces without the need for special adapters, which simplifies future maintenance.

Influence of material and corrosion on lifespan

The material of the connection has a decisive impact on resistance to corrosion, especially if the pressure gauge is located in an environment with high humidity or chemically aggressive substances. Common steel connections with a chrome finish are suitable for dry areas, whereas stainless steel connections (AISI 316 stainless steel) are essential for outdoor installations or systems with coolant containing salts. Corrosion on the threads is one of the most common causes of pressure gauge damage, as it gradually destroys the sealing surfaces and causes leaks that cannot be repaired simply by tightening.

Chromed steel is sufficient for indoor areas with normal humidity.
Stainless steel connections are recommended for boiler rooms with high humidity.
A thermometer with a pressure gauge requires more durable materials due to thermal expansion.
Regular inspection of the thread condition extends the life of the device by years.
Combining different metals (galvanic cell) accelerates corrosion and should be avoided.

If you need to monitor not only pressure but also temperature in the system, we recommend the axial thermopressure gauge 0°C - 120°C 0 - 6 bar, 63 mm, which combines both functions in one robust body with a stainless steel connection. This type is ideal for modern condensing boilers, where it is necessary to monitor the temperature regime and pressure simultaneously, with the stainless steel connection ensuring long-term stability even during frequent temperature cycles.

Mounting procedures and seals

Regardless of the selected connection diameter, it is crucial to correctly choose and apply the sealing material. For standard water systems, gasket seals or Teflon tapes are most commonly used, which ensure a hermetic seal without damaging the threads. When mounting an axial pressure gauge, it is important that the seal is not located in the threads, but on the lower surface of the connection, where tightening occurs. Using an incorrect seal, such as a rubber ring instead of a gasket, can lead to it being extruded at higher pressure and subsequent leakage.

A common mistake is over-tightening the Teflon tape, which can get inside the manometer and block the moving parts. When installing the axial thermometer 0°C - 120°C, 100 mm, it is important to ensure that tightening does not damage the glass or internal mechanisms, so it is recommended to use a torque wrench or tighten manually until the rotation stops. Proper installation also includes checking the levelness of the instrument to prevent spring deformation due to gravitational forces.

Connection with straight and tapered thread

While most standard manometers use the standard internal G thread, there are also models with external metric M thread, which are often found in older boilers or specific industrial equipment.

Frequently asked questions

What is the standard connection size for a 63 mm manometer?

The standard for this size is a 1/8 inch G thread, which is sufficient for typical home heating systems and most boilers.

Can I use a reducer if I have a different connection?

This is technically possible, but not recommended, as it reduces measurement accuracy and increases the risk of leaks or instrument failure.

Why does the manometer show zero even though there is pressure in the system?

The cause may be a clogged connection, faulty sealing, or damaged spring, which is often related to incorrect installation or the age of the device.

Choosing the correct size and type of connection for a 63 mm manometer is the basis for the safe and accurate operation of your heating system, which should always be adjusted according to the specific requirements of the boiler and system.

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.