Brine loop leak check without digging: pressure test and tracer gas steps

Part of our guide on how grants affect heat pump prices

Check for brine loop leaks using pressure tests, tracer gas detection, and pump monitoring without costly ground excavation.

How to perform a pressure test on a brine loop

A pressure test involves filling the brine loop with water or antifreeze solution and pressurising it to about 3-5 bar (300-500 kPa). This pressure should be stable but depends on your system’s design and manufacturer's specifications, so check your heat pump manual first.

Attach a calibrated pressure gauge to the loop’s test port and isolate the system from the heat pump. Then pressurise the loop using a hand or electric pump. Leave the system sealed for at least 24 hours while monitoring the gauge for any pressure drop.

A pressure drop of more than 5% over 24 hours usually indicates a leak. Minor fluctuations can occur due to temperature changes or trapped air but should stabilise quickly. Repeat the test if unsure, after bleeding air from the system.

If the system cannot hold the test pressure, locate the low point and visually inspect accessible pipework for signs of moisture or damage before considering excavation. If that sounds like your situation, read up on heat pump planning permission permitted development rules uk next.

Using tracer gas to detect leaks without excavation

Tracer gas detection involves injecting a non-toxic, easily detectable gas such as helium or a hydrogen-nitrogen mix into the brine loop. This gas escapes through leaks and is detected by sensors above ground or in accessible areas.

Helium is preferred for its small molecule size, allowing it to escape even tiny leaks. Hydrogen mix is commonly used as a cheaper alternative but can be less sensitive. The choice depends on availability and budget.

Specialist equipment is required to safely inject and detect tracer gas. Detection sensors scan the soil above the loop for gas concentrations, pinpointing leak locations without disturbing the ground. Before you commit to anything, it is worth looking at central heating installation steps.

Tracer gas detection is highly effective for locating leaks but usually requires hiring a contractor specialising in heat pump or geothermal system diagnostics.

Before injecting tracer gas, it is essential to fully evacuate the existing fluid from the brine loop to ensure the gas disperses evenly and is not diluted by residual liquid. The injection pressure typically ranges from 2 to 4 bar, depending on loop length and pipe diameter, to avoid damaging the system. After injection, sensors scan systematically at intervals of about 0.5 to 1 meter above ground, focusing on suspected leak zones identified by pressure tests or visual signs.

In some cases, tracer gas may accumulate in soil fissures or pockets, causing delayed detection. To confirm a leak, technicians may conduct repeated sweeps over several days, especially after rain, which can affect gas migration. Detection sensitivity can identify leaks as small as 0.1 mm in diameter, considerably reducing the risk of missing minor but impactful leaks.

Signs and monitoring to confirm a leak without ground disturbance

You can monitor your circulating pump’s pressure and flow rate as indirect leak indicators. A steady pressure or flow drop of more than about 10% without external changes usually suggests brine loss through leaks.

Check your heat pump’s control panel for fault codes related to low pressure or flow in the ground loop. These errors often trigger before physical damage is visible.

Visible signs include soggy patches or frost spots on the ground above the loop, but these may be subtle or absent if the leak is deep or under hard surfaces.

Regularly recording pump pressures and temperatures helps spot trends. Sudden unexplained drops coincide with leaks, while stable readings reduce suspicion.

If you suspect a leak but can’t confirm it by monitoring, proceed to pressure or tracer gas tests before digging.

Temperature monitoring of the ground surface above the brine loop can also aid in leak confirmation. A leaking loop often cools the surrounding soil, detectable by infrared thermography or handheld thermal cameras. Temperature differentials of 2-4°C compared to adjacent areas can point to leak locations without excavation.

Additionally, changes in the heat pump’s coefficient of performance (COP) over time may indicate loop leaks. A drop of 5-10% in efficiency, unexplained by external factors, suggests brine loss reducing heat transfer effectiveness. Combining these indirect signs helps build a reliable case before invasive investigation.

When to call a contractor for leak detection

If your pressure test fails, tracer gas equipment is unavailable, or monitoring shows suspicious signs, call a qualified heat pump or geothermal specialist. They have the tools and expertise to confirm leaks and recommend repairs.

Early professional assessment can save money by pinpointing leaks precisely, preventing unnecessary ground excavation or system damage.

Contractors also handle safely re-pressurising and refilling your brine loop, ensuring correct antifreeze mixtures and pressures for optimal heat pump performance.

Use only certified professionals familiar with UK heat pump and ground loop standards to comply with building regulations and warranty requirements.

How circulating pump pressure checks help find brine leaks

The circulating pump maintains steady pressure and flow in the brine loop, typically between 1-3 bar depending on pipe length and system size.

Leaks cause the pump to work harder as fluid escapes, leading to lower pressure readings and reduced flow rates.

Regularly note pressure gauge and flow meter readings during operation and compare to manufacturer baselines. A consistent drop of 10% or more without other faults indicates potential leaks.

Other causes like clogged filters or pump wear can mimic leak symptoms, so confirm with pressure test or tracer gas before excavation.

How to check a brine loop for leaks without digging

To check a brine loop for leaks without digging, first perform a pressure test by isolating and pressurising the loop to 3-5 bar and monitoring for pressure loss over 24 hours.

Next, monitor the circulating pump pressure and flow for unexplained drops greater than 10%, which often indicate leaks.

If these steps suggest leaks but do not reveal location, use tracer gas injected into the loop and detect escaping gas with specialised sensors above ground.

If you are unsure how to execute these tests or lack suitable equipment, call a qualified contractor to avoid damaging your system or property.

Following this stepwise approach saves money by reducing unnecessary ground excavation and preserves your heat pump’s efficiency.

For short loops under 50 meters, a pressure drop of 5% over 24 hours can indicate a significant leak, whereas longer loops may show smaller relative drops due to larger volume. Check manufacturer guidelines to interpret pressure loss in context.

If a leak is suspected but not confirmed after initial tests, consider isolating sections of the loop using valves if available. Testing smaller segments separately can isolate the problem area, reducing the search scope and need for digging.

When performing these checks, always ensure the antifreeze concentration is adequate to prevent freezing during testing, especially in cold weather. Low antifreeze levels can lead to false pressure drops or damage, so verify fluid properties before starting.

1. Isolate and fill the brine loop with fluid.
2. Attach a calibrated pressure gauge and pressurise to 3-5 bar.
3. Monitor the pressure gauge for 24 hours for drops greater than 5%.
4. Check circulating pump pressure and flow during normal operation for drops over 10%.
5. If leaks suspected but location unknown, arrange tracer gas injection and detection.
6. Call a professional if any test is inconclusive or complicated.

Questions people still ask

Having installed and maintained brine loops myself, I recommend pressure testing and pump monitoring as your first leak detection tools—they save time and avoid unnecessary digging.