In many homes across Tallinn and Harjumaa, a bathroom towel rail holds both practical and aesthetic importance—it dries towels, helps protect the bathroom from moisture damage, and provides additional warmth to the space. Therefore, it's particularly frustrating when the unit heats unevenly: one part is hot, while another is lukewarm or even cold.
Uneven heating isn't merely a matter of comfort. It can indicate a problem that may worsen over time—such as sludge accumulation or a valve malfunction—potentially leading to a leak or the complete failure of the unit.
In this guide, we'll explain the difference between central heating and electric towel rails, what problems each type typically causes, and provide a step-by-step guide on how to diagnose the issue yourself and when to call in a specialist.
Two Main Types: Hydronic (Water-Fed) and Electric Towel Rails
Before delving into the causes, it's worth clarifying which type of towel rail you have in your bathroom, as this largely determines which fault is more likely.
A hydronic towel rail, connected to the central heating system, works similarly to a regular radiator—hot water from the house's heating or hot water circulation system flows through it. An electric towel rail, however, heats up using a built-in heating element connected to the electrical grid, with its temperature regulated by a thermostat. There are also dual-fuel models that can operate via the central heating system during the heating season and electrically in summer.
- Hydronic towel rail — problems are usually related to air, valves, sludge, or installation angle.
- Electric towel rail — problems are typically related to the heating element, thermostat, or electrical connection.
- Dual-fuel towel rail — can exhibit problems from both types, depending on which mode the unit is currently operating in.
Air Inside the Towel Rail – The Most Common Cause of Uneven Heating
If your hydronic towel rail is heating only at the bottom, while the upper pipes remain cold or lukewarm, the most probable cause is air accumulated in the upper part of the unit.
Towel rails often have complex designs—a ladder-like structure with multiple parallel pipes—and air tends to collect in the highest and furthest points, where water circulation struggles to push it out. Since air is lighter than water, it remains trapped in the upper pipes, obstructing the flow of hot water there.
How to Bleed a Towel Rail
Most towel rails have a small bleed valve at the top, which opens with a special key or screwdriver, just like a standard radiator. Before bleeding, it's advisable to turn off the heating momentarily, place a cloth or small container under the valve, and carefully open the valve until you hear a hissing sound. Once a steady stream of water emerges without air bubbles, close the valve.
If bleeding doesn't help, or if air repeatedly returns within a short period, it likely points to a larger issue in the heating system—such as problems with the expansion tank pressure or continuous air ingress into the system, which we cover in more detail in our article about air accumulating in radiators.
Partially Closed or Stuck Valve
If your towel rail is warm on one side and cold on the other, or if the entire unit is lukewarm, you should check the inlet and outlet valves. If one of the valves has been accidentally partially closed—for example, after repair or maintenance work—insufficient hot water will flow through the unit.
In older valves, the spindle may also seize over time, even if the handle appears to be in the open position. In such cases, the handle moves, but the actual water flow remains obstructed.
- Check that both valves (flow and return) are fully open.
- Feel the valves by hand—if one side of the pipework is significantly colder immediately after the valve, the problem might be there.
- If the valve feels stiff or doesn't move at all, do not force it—call a specialist to assess whether the valve needs servicing or replacement.
Accumulated Sludge and Debris Inside the Pipework
Over the years, rust and limescale accumulate in the heating system water, settling in lower parts of pipes and areas where water flow is slower. The complex design of a towel rail creates precisely these conditions, making sludge a common problem, especially in older houses and apartment buildings.
When sludge accumulates, it's typical for the unit to have initially heated evenly, but over time, the heating becomes increasingly uneven—this distinguishes a sludge problem from air, which usually appears more quickly and is easily remedied by bleeding.
We also discuss the issue of sludge more broadly in the article on heating system dirt and sludge, as it affects not only towel rails but also radiators and the overall lifespan of the pipework.
How to Detect Sludge Yourself
If, upon touching your towel rail, you feel that some pipes are noticeably warmer than others and the difference doesn't disappear after bleeding, it's likely due to sludge. The definitive diagnosis and solution usually require flushing the unit or the entire heating system, which is best entrusted to a specialist.
Incorrect Installation Angle and Obstruction of Air Release
Hydronic towel rails and their supply pipes usually require a slight incline to allow air to naturally move to the highest point, where it can be released through the bleed valve. If the installation is done without a correct incline or bleed point, air will repeatedly accumulate in the system, causing persistent uneven heating that won't disappear even with regular bleeding.
This problem is particularly common when a towel rail has been installed by a DIYer or an inexperienced installer who did not account for the principles of natural circulation and air movement in the heating system.
- If air repeatedly returns after bleeding within just a few days or weeks, suspect the installation angle.
- If the towel rail was installed within the last year and the problem has been present from the start, consider calling back the installer under warranty.
- Correcting the angle typically requires repositioning the pipework, which is a job for a specialist.
Thermostat and Heating Element of an Electric Towel Rail
For an electric towel rail, the cause of uneven heating is not air or sludge, but typically a fault in the heating element or thermostat. Since the heating element is usually located at the bottom of the unit and heat spreads upwards through natural convection, uneven heating often means that the heating element's power has decreased or the thermostat is switching the unit off too early.
If an electric towel rail initially heats well but switches off quickly and cools down before the entire unit can heat evenly, it's likely due to an incorrect thermostat setting or a malfunction.
What to Pay Attention to with an Electric Unit
Check that the unit's power cord and plug are in good condition and that the thermostat knob or display responds normally. If the unit doesn't switch on at all, or switches on and off very frequently in short intervals, it's likely an electrical fault. You should not attempt to disassemble the unit yourself, as it is an electrical appliance in a damp environment.
Incorrectly Sized or Underpowered Towel Rail
Sometimes, the cause of uneven heating isn't a fault, but simply that the unit itself is incorrectly chosen for the bathroom's size or the heating system's capacity. A towel rail with too large a surface area, or whose diameter and pipework are too long for low water flow, may never heat completely evenly, even if everything else is in order.
This is particularly common in situations where an old, small towel rail was replaced with a much larger model, but the heating system's pipework or pump settings were not adjusted to meet the new unit's needs.
Specifics of Apartment Building Central Heating Systems
In an apartment building with a central heating system, individual apartment owners usually cannot directly influence the system's overall pressure or circulation speed, which directly affects towel rail heating. If the problem occurs only in one apartment, it is more likely to be a local cause—such as a valve, air, or sludge within that specific unit.
However, if several neighbours in the same building complain about similar issues, such as uneven heating of towel rails or radiators, it's worth contacting the apartment association or building manager, who can arrange a more comprehensive inspection of the heating system. We discuss such central heating system pressure and circulation changes in more detail in the article about heating system pressure fluctuations in winter.
Another common problem in apartment buildings is general pipework ageing affecting all units simultaneously—we delve deeper into this in the article on the lifespan of apartment building heating pipework.
Step-by-Step Guide: How to Diagnose the Problem Yourself
Before calling a specialist, it's worthwhile to go through a few simple steps that can help narrow down the problem and save time later.
- Step 1: Identify whether your towel rail is hydronic, electric, or dual-fuel—this determines where to look next.
- Step 2: Feel with your hand which parts of the unit are warm and which are cold—is it the top, bottom, left, or right side?
- Step 3: If it's a hydronic unit and the top is cold, try bleeding it.
- Step 4: Check that both valves are fully open.
- Step 5: Observe whether the problem repeatedly returns after bleeding—this indicates an installation angle issue or continuous air ingress.
- Step 6: For an electric unit, check the power cord, plug, and thermostat response.
- Step 7: Note when the problem first appeared—was it immediately after installation, gradually over years, or suddenly—this information will help a specialist diagnose the cause more quickly.
When Is It Time to Call a Specialist?
Some problems, such as simple bleeding or opening a valve, can be resolved yourself. However, several situations definitely require the assistance of an experienced specialist.
- If bleeding doesn't help or air repeatedly returns quickly.
- If you suspect sludge or debris inside the pipework.
- If a valve is stiff, seized, or doesn't respond at all.
- If an electric unit doesn't switch on or switches on and off too frequently.
- If you suspect an incorrect installation angle or a faulty connection from the start.
- If the problem occurs in multiple apartments simultaneously in an apartment building.
How ToruFix Can Help
During heating system maintenance, we inspect towel rail and radiator valves, bleed the system, and, if necessary, flush sludge from the pipework. If the unit is too old, incorrectly sized, or irreversibly damaged, we also assist with towel rail or radiator replacement and installation.
How to Prevent Uneven Heating in the Future
Many problems can be prevented with regular maintenance and correct initial installation.
- Bleed your towel rail at the start of the heating season along with other radiators.
- Periodically check that both valves are open and move freely.
- Have the heating system flushed if you notice increasingly worsening uneven heating.
- Choose a towel rail size and power appropriate for your bathroom size and the existing heating system's capacity.
- Entrust installation to an experienced specialist who will account for the correct angle and bleed point location.
- For electric units, follow the manufacturer's maintenance instructions and avoid using the unit with wet hands or a damaged cord.
Connection to Bathroom Moisture Damage
An unevenly heating or completely non-functional towel rail means the bathroom remains damper and towels dry slower, which in turn promotes moisture and mould formation in the room. This is especially critical in small and poorly ventilated bathrooms, where the towel rail plays a vital role in reducing moisture in addition to heating.
If your bathroom suffers from moisture regardless of the towel rail's condition, it's worth reading our comprehensive guide on preventing bathroom moisture damage, where we discuss ventilation, waterproofing, and other moisture-related factors.
How Usage Habits Affect Towel Rail Heating
Uneven towel rail heating isn't always due to a technical fault—everyday usage habits can also cause or exacerbate the problem. For example, if thick terry towels or a full load of laundry are constantly hung on the towel rail to dry, this obstructs heat radiation into the room, creating the impression that the unit is weaker than it actually is.
Similarly, thermostat usage directly affects how evenly an electric or dual-fuel unit heats. If the thermostat is set too low, the heating element may never sufficiently heat all parts of the unit, leading to the perception of uneven operation, even though it's simply a matter of settings.
Outside the heating season, when a hydronic towel rail is not heated, it may feel completely cold—this is entirely normal and does not indicate a fault if the house's general heating is also turned off. This often causes confusion during transitional periods in spring and autumn when heating is on some days and off on others.
- Avoid consistently hanging thick towels and clothes across the entire unit, as this obstructs the free radiation of heat into the room.
- Check the thermostat setting of an electric or dual-fuel unit before concluding that it's faulty.
- Remember that during the non-heating season, a hydronic towel rail may be completely cold without indicating a problem.
Specifics of Dual-Fuel Towel Rails
A dual-fuel towel rail, which operates via central heating during the heating season and electrically in summer, requires special attention because it has two separate systems, both of which can cause uneven heating. Confusion often arises when the unit works well in water mode but is weaker in electric mode, or vice versa.
For a dual-fuel unit, it's crucial to know which mode is currently active, as the troubleshooting steps differ completely—for water mode problems, check valves, air, and sludge; for electric mode problems, check the heating element and thermostat. On some models, switching modes requires manually turning a valve, and if this valve remains in the wrong position, the unit may appear not to work at all, even though the wrong mode is actually active.
If you're unsure which mode your dual-fuel towel rail is currently in, it's worth checking the unit's user manual or contacting the installer who can explain how the mode switching works for your specific model.
Does Uneven Heating Increase Heating Costs?
An unevenly heating towel rail can, in the long run, increase both heating and electricity costs, depending on the unit type. If a hydronic unit doesn't heat properly due to air or sludge, the heating system often compensates by increasing the overall flow temperature, which raises the heating costs for the entire house, not just for that one unit.
For an electric unit, a faulty thermostat can cause the unit to switch on and off too frequently, consuming more electricity than a smoothly operating system, even if the end result appears similar to the user—a lukewarm towel rail.
Therefore, uneven heating should not be regarded merely as a comfort issue, but also as a financial one, which becomes increasingly significant over time if the problem remains unresolved and worsens.
Even a small amount of savings realised from an evenly operating heating system is noticeable over time—especially in apartment buildings where heating bills are distributed among flats based on consumption, meaning the inefficiency of a single unit can affect neighbours' heating bills if the problem is related to general circulation.
Unit Age and Material's Impact on Heating
The age of a towel rail plays a significant role in its susceptibility to uneven heating. Older units, in use for over ten years, are naturally more prone to internal rusting, valve wear, and seal deterioration, all of which can individually or together cause a gradually worsening problem.
The material from which a towel rail is made also affects long-term durability. Stainless steel units are generally more resistant to internal corrosion than cheaper alloy steel or chrome-plated steel models, which can narrow due to rust internally and accumulate sludge more quickly over time.
If your towel rail is quite old and problems recur despite regular maintenance, it's worth considering whether it's more sensible in the long run to invest in a new unit rather than repeatedly repairing ageing pipework and valves that are likely to cause problems again in the near future.