1st Choice Gas Services

likely causes & diagnoses:
1. faulty or sluggish circulation pump
• if the pump isn’t circulating hot water efficiently, it may struggle to push water upstairs — especially when demand is high or the system is partially sludged.
• diagnosis tip: feel the pump housing. is it hot? is it vibrating or silent? a weak or seized pump can allow partial heating downstairs but fail to reach upstairs consistently.
2. partially blocked system / sludge build-up
• over time, sludge (magnetite) builds up and restricts flow, especially in upstairs pipework or older systems.
• diagnosis tip: check if upstairs rads take much longer to heat than downstairs — or feel cooler at the bottom. a power flush or magnaclean install may be needed.
3. unbalanced system
• even if all valves are open, radiators need balancing to ensure even heat distribution — otherwise, water takes the path of least resistance (usually downstairs).
• diagnosis tip: try partially closing lockshield valves on the downstairs radiators to force more flow upstairs.
4. pump settings or wrong speed
• some newer boilers or system pumps have adjustable speeds. if set too low, they may not circulate water strongly enough to upstairs rads.
• diagnosis tip: check pump speed settings (if accessible) — increase to medium or high if it’s on low.
5. zoned heating valve fault (if applicable)
• if you have a two-zone system (upstairs/downstairs), a stuck or intermittent motorised valve could be the issue.
• diagnosis tip: check if your system uses motorised valves (usually near the hot water cylinder or boiler), and listen/feel if the upstairs zone valve is opening properly when demand is present.

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recommended next steps:
• start by trying system balancing (adjust lockshield valves downstairs).
• then inspect the circulation pump for noise, heat, or signs of weakness.
• if the issue persists, consider a power flush or at least a chemical cleanse of the system.
• if zoned, test or replace the motorised valve controlling upstairs flow.

let me know what boiler make/model you’re running or if you want a step-by-step to test the pump or balance the rads — happy to walk you through it.

???? will the heating still work if the water mains is turned off?

? yes – in most cases, the central heating system will continue to function even with the mains water turned off, as long as:
1. the boiler and heating system are sealed (pressurised combi or sealed system boiler), and
2. the system is already full of water and holding pressure before you turn off the mains.


???? here’s how it works:
• modern boilers (combi or system) operate using the water already inside the heating loop (radiators and pipework), not a continuous supply from the mains.
• the mains is only needed to top up pressure in sealed systems — which you’ve already done after bleeding.
• so, turning off the mains will not stop your heating from running on its timer — it will circulate the existing water through the system.


?? exceptions / things to check:
1. open-vented system (with loft tanks)
• if the property has an older boiler with a feed-and-expansion tank in the loft, it relies on the mains to keep that tank topped up.
• turning the mains off could eventually result in air ingress or system drain-down over time.
2. frost protection & leaks
• if a leak develops while the heating runs and the pressure drops, you won’t be able to repressurize the system with the water mains off.
• in winter, if your system relies on frost protection, make sure some flow is possible and that the boiler won’t fault due to low pressure.


? best practice for unoccupied homes:
• turn off the mains at the internal stopcock, but consider installing an auto-stop leak valve or leak detection system for extra peace of mind.
• leave the heating on a timer or frost setting, and check that system pressure is good before leaving.
• if you’re unsure whether the system is sealed or open-vented, look for:
• a pressure gauge near the boiler = sealed system
• a small storage tank in the loft = open-vented (needs water on)

let me know your boiler model or if you’re unsure about the system type — i’ll help you confirm.

? quick summary of your concerns

1. ???? energy consumption

yes — low system pressure can reduce the efficiency of your heat pump, for these reasons:
• poor heat transfer: low pressure = less water in the system, which reduces the amount of heat the pump can transfer into your home.
• increased run time: the system may need to run longer to reach the set temperature, using more electricity.
• hot water tank recovery time may increase, requiring more frequent cycling.
• air pockets from low pressure or tiny leaks can trap heat in the system, leading to pump strain or short-cycling.

so, yes — running with low pressure over time can increase your energy bills, reduce comfort, and put extra wear on the system.

2. ???? why does the pressure keep dropping?

repeated pressure drops usually point to one (or more) of these issues:

???? common causes:
1. micro-leak in the system
• small, often hidden leaks in pipework, radiator valves, or joints (especially under floorboards or behind units).
2. leaking pressure relief valve (prv)
• if the system was overfilled at any point, the prv may be weeping small amounts of water as a result.
3. expansion vessel failure or loss of charge
• the expansion vessel is crucial for regulating pressure as water heats and expands. if it fails or loses air charge, pressure will drop.
4. air removal over time
• if air is slowly bleeding out of auto air vents, pressure can drop gradually without any visible water loss.

???? diagnostics & fix suggestions

???? diagnostic steps:
• check for visible leaks around radiators, pipes, and under hot water cylinders.
• ask the landlord’s engineer to test or recharge the expansion vessel.
• inspect the prv pipe (usually outside) — if water is dripping out periodically, the valve may be letting pressure out.
• confirm whether auto air vents or towel radiators are constantly bleeding air.

????? suggested fixes:
• if no obvious leak: request a pressure drop test with leak detection fluid or thermal imaging.
• have a qualified tech check the expansion vessel — it might need recharging with air or replacing.
• fit a leak detection fluid or inhibitor with dye into the system if the leak is very small/hard to trace.
• in extreme cases, consider installing a sealed system alarm to notify when pressure drops — especially in rented or vacant properties.

????????? what to tell the landlord:

politely inform them that:

“the system pressure drops frequently, which could be reducing the efficiency of the heat pump and increasing electricity use. it’s also a sign that something is wrong — possibly a failing expansion vessel or a small leak. i’d appreciate a more in-depth inspection to avoid long-term cost or damage to the system.”

?

if you can give me the heat pump brand/model, i can give you exact pressure ranges and specs for your system. let me know — happy to assist further!

To repressurise a glow-worm compact 24c combi boiler, follow the simple steps below. this is a common issue after bleeding radiators, as air release causes the pressure to drop.

???? how to repressurise your glow-worm compact 24c boiler

???? what you’ll need:
• access to the filling loop (usually a silver braided hose beneath the boiler)
• a watchful eye on the pressure gauge (should be visible on the front panel)

? step-by-step instructions:

1. locate the filling loop
• look under the boiler for a flexible braided hose connecting two copper pipes.
• on either end of this hose, there will be one or two black or grey tap-style valves (or flathead screwdriver-style).

2. ensure boiler is off and cooled
• turn off the heating and allow the system to cool if it’s been running.
• this gives a more accurate pressure reading.

3. open the valves slowly
• turn both valves (if there are two) slowly to the open position (quarter turn usually).
• you should hear water flowing into the system.

4. watch the pressure gauge
• keep an eye on the gauge — your target is between 1.0 and 1.5 bar.
• as soon as it reaches the target zone, close both valves immediately.

5. restart the boiler
• turn the boiler back on and reset it if needed.
• check for normal operation — heating and hot water should now work as expected.

?? important notes:
• never over-pressurise: if you go above 2.5 bar, the pressure relief valve may open.
• if the system keeps losing pressure, it may indicate a leak or failing expansion vessel.
• if you’re unsure whether the filling loop is internal or external, check the manual or send a photo — some models have an integrated filling link.

let me know if you’d like a diagram or if you’re not seeing the filling loop under your boiler — happy to guide you through with a photo if needed.