Radiator cold at the bottom

When the outside temperature drops significantly, we dream of returning to a warm apartment, even after a short walk. However, if it turns out that it is also cold there, and we will frostbite faster than we warm our hands by the radiator, we need to consider what is the reason for this. Once we have located the problem, we can move on to solving it.

Check out our ultimate guide on fixing cold radiators to help you diagnose more cold radiator problems.

Radiator does not heat up – check the radiator thermostat

Sometimes the simplest solutions are the least obvious. Therefore, before we start looking for serious faults, let’s set the radiator knob to the maximum and wait a longer moment, e.g. an hour. During this time, the radiator should warm up – if not, there is a problem somewhere. However, you don’t have to worry in advance, as it doesn’t necessarily mean that your thermostat is broken. Symptoms that bother us can probably be removed by yourself.

Radiator thermostats are mounted on pipes that supply hot water to the heating device. Their task is to regulate the temperature in the rooms, which is possible thanks to the continuous control of the liquid supply by closing and opening the valve. Therefore, if the radiator remains cold, despite the fact that we are diligently turning the tap, our further actions should start with the answer to the question of how to check the thermostat. Thanks to this, we may avoid additional work put into looking for a more serious failure.

One of the most common situations where a radiator thermostat is not working as it should is when it is not used for a long time – for example during the spring and summer period. It happens that the valve needle gets blocked, so that hot water does not reach the radiator. Then this tiny element has to be released, which is quite a simple activity. We start by getting to the valve – for this we unscrew and remove the thermostatic head. You will immediately notice a protruding needle, which you should grab with pliers and gently pull it towards you, thereby unlocking it. As a result, the radiator with the thermostat should start working properly.

If this does not help, the presetting on the thermostatic valve may not be set correctly, causing the water flow to be too low again. This time, however, we recommend caution when trying to repair it yourself, as a change within one radiator may affect the operation of the entire installation.

The heating system is not working. Radiator Cold at the Bottom? Fix It! Drink hot water.  radiator sludge

If it is an undamaged thermostat that causes our problems, it may be the result of a lack of water in the radiator. To find out about this, you need to inspect the drain valve, which should be unscrewed. Look for it at the bottom of the radiator – next to the exit, under the hexagonal nut. How to unscrew the bottom valve of the radiator ? Just use an Allen key.

Radiator cold at the bottom

When the radiator does not heat up properly, e.g. if the radiator heats up halfway or we hear gurgling, sound of overflowing water or noise, air may have become in it.

Air that has leaked into the central heating system in an excessive amount, as a result of e.g. assembly errors or leaks, may interfere with its operation. The water pressure is then too low, which will result in cold radiators or uneven heat distribution .

Importantly, low liquid pressure does not have to be caused by air in the system. It is possible that one of its elements has been damaged (so that water escapes from the central heating), or it is poorly selected, at least in terms of power.

The pressure gauge will inform you about the pressure in the system – the gauge should be in the area that determines the optimal number of bars. If the pressure turns out to be too low, it will be necessary to roll up your sleeves to work. How to fill the radiator with water ? Living in a detached house, we can undertake this task ourselves, remembering to refill the fluid level as slowly as possible, and then bleed the radiators throughout the circuit. However, if the problem is the cold radiators in the block, you should report your doubts to the caretaker or a representative of the housing cooperative, who will know what to do next.

How to bleed the radiator?

Air in the heater can be caused by several factors, and incorrect water pressure is only one of them. The problem also arises if the installation was incorrectly designed or made, and its elements are leaky. This not only results in our thermal discomfort, but can also cause corrosion in the installation. Processes inside the pipes due to the presence of air will result in the appearance of rust and deposits which may then block the flow of water. 

What to do when there are cold spots on the radiator? An air in a radiator in a block of flats or a house is not a serious fault and we can try to deal with it ourselves. The entire process for manual air vents is quite similar with different types of radiators, though there are some key differences. However, the basis is always to turn off the thermostat on the radiator and wait until it is cold. If the troublesome device is not equipped with a thermostat, the water supply to the installation should be cut off. Which radiator should I start venting? From the one closest to the boiler.

Cold radiator, cold at the bottom?  Your Radiator Cold At The Top? If you notice your radiator is cold at the top and hot at the bottom, you will need to bleed your radiator to remove the trapped air inside.

When should we bleed the radiators?

The optimal months to purge the radiators are September and October, just before the strong heating season begins . It is convenient not to wait for the temperatures to drop and we need the heating, since if we have not purged it before, it will work “at half gas”, with the consequent waste of energy and money.

How to bleed the radiators step by step

Purging is a relatively simple process that anyone can do at home by following these steps:

  1. Check if you need to bleed your radiators. Turn on the heat and run your hand over the top of the radiator: if this top part of the radiator is cooler than the bottom part, this means that it has air (remember that air tends to rise). Purging is done with the boiler off and the radiators cold .
  2. Head to the radiator closest to the boiler . The following operations must be followed starting from the radiator that is closest to the boiler, following the natural flow of water.
  3. Place a container under the faucet. Take a saucepan or a glass and place it under the faucet. In this way, you will prevent the floor from getting wet when the purging water begins to come out.
  4. Turn the key with a screwdriver. You can also use a coin to open the valve faucet. The faucet opens and air (smelly) begins to come out along with some water, but the flow will not be uniform.
  5. Close the tap when the jet is fluid. When the jet of water that comes out is completely fluid, it means that the air has already come out, so the tap can be closed by turning in the opposite direction.
  6. Repeat the operation on all the radiators . Remember to follow, radiator to radiator, the flow of the water. And of course, if any radiator of the circuit is cancelled, it is not necessary to carry out this operation.
  7. Check the boiler pressure (1 – 1.5 bar) . Always after finishing the purging of each radiator we must check that the pressure of the boiler is between 1 and 1.5 bars, before continuing with the next one, since after purging the pressure level usually drops. We must make sure that the pressure is between these levels.
Radiator cold at the bottom. Turn off your entire heating system and check.
Locate your thermostatic radiator valve.
This is quick and easy guide to central heating inhibitor.
The best way to remove sludge from the bottom of a radiator is to give it a power flush.
Completely cold radiator.

To professionally bleed the radiators and guarantee a correct hydraulic balance of the installation , we must first close the radiator water inlet with a key (the lockshield located at the bottom, where the tube connects to the appliance ). ). We will repeat the bleeding operation by opening the valve with the screwdriver but this time we will wait for all the water to come out of the radiator until the air comes out.

At this moment, we open the water faucet a little so that it begins to fill again, with which a stream of water will come out again. We closed the petcock and left that radiator closed. In this way, we already have the radiator purged at 100%.

As we have mentioned, between purging one radiator and another, it is advisable to check the pressure of the boiler . We empty, purge, close and check the pressure, one by one. We remember that we must start purging from the radiator closest to the boiler in our heating circuit.

When there are two radiators left, we will close one of them so that the boiler will be working with one radiator. We’ll purge it and then open it up to purge the other one we have left, always making sure at least one radiator is working. When we have those two radiators working and we see that there are no noises, we will gradually open them all to check if any of them emit any sound, in case there is some air left in the pipe.

How to bleed a cast iron radiator ? 

The preparations are basically the same, but the lack of a valve for venting the radiator means that we will work with a screw connection. We gently loosen it until we hear air escaping. If you do not want to flood the room with a stream of water, you have to act very carefully. When only water is dripping from the radiator, turn off the flare nut.

The radiator does not heat up after venting

If the stove heats up and the radiators remain cold or are lukewarm despite venting, topping up water or checking the thermostat, they may have been installed incorrectly or connected inversely. The problem may also lie in the furnace itself or the heating ducts, as evidenced by e.g. a cold radiator only at the bottom .

There are many options, so when the radiators do not heat up, it is a good idea to report the failure to a housing association or, in the case of a single-family house, call a plumber. A specialist will certainly quickly cope with an unscrewed drain valve or too low presetting, which may not be so obvious for the average Kowalski. It will also verify that the heater temperature controller is working properly and that the program on the stove is properly set.