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Choosing the right dehumidifier

A dehumidifier is, in general, a household appliance that reduces the level of humidity in the air. Humid air is, in fact, the optimum environment for various pests (including clothes moths, fleas, cockroaches, woodlice and dust mites) and the development of mould and mildew within homes, which can both pose a range of health risks. Very damp climates can also be extremely uncomfortable for countless numbers of people, causing excessive sweating that can't evaporate due to the already-moisture-saturated air as well as cause condensation that can disrupt sleeping. 

"" provides a range of dehumidifiers to deal with a wide variety of moisture-related problems in the domestic, commercial and industrial environments. All our dehumidifiers are made in an extremely resourceful and versatile way, meaning they can be used anywhere and anytime. Our dehumidifiers can remove three times more moisture than a heater, for the same energy costs, thus in the commercial and industrial worlds a dehumidifier can be of huge benefit to an employer. Our dehumidifiers reduce costs due to condensation damage, as well as promote a healthy atmosphere amongst the workforce, which can only increase their productivity. 

There are the two main groups of Dehumidifiers: Refrigerant Dehumidifiers and Desiccant Dehumidifiers.

Refrigerant Dehumidifiers

One of the two main types of dehumidifier is a refrigerant coil technology dehumidifier. These work by condensing moisture out of the air. Damp air from within the room or building is drawn into the dehumidifier and passed over a cold evaporator coil which cools the air below its dew point temperature.  This results in the condensation that can be collected from the cold coils in liquid form.  This water is collected in a pan and either removed manually or through a specially made hose by which the water is automatically purged. The dry air in the machine is then passed over warm condensing coils, heating the air again before exiting the machine.  This dry air is, in many machines, pushed out at pressure so can be directed at specific damp areas to accelerate drying. 

Desiccant Dehumidifiers

Another commonly used type of dehumidifier is a desiccant dehumidifier. These operate by passing the moist air through a rotor which contains moisture adsorbent desiccant material.  Once water is taken from the air by the absorbent material, dry air can be blown back into the building, thereby further encouraging drying.  Water collected within the desiccant wheel is removed by adding heat so the vaporised moisture can then be ducted out of the building. The desiccant material, which draws in the moisture from the air, is typically silica gel. The type used is not of the usual ‘gel’ texture but is rather a permeable form of granular silica. These can absorb the dampness from the air by attracting it within each granule.  It is then by the addition of heat that this moisture can then be released from the silica gel by evaporation and pushed out of the building, leaving the desiccant wheel ready again to collect further moisture.

Comparing Performance

1. Extraction Rates:

One of the main benefits of our refrigerator coil dehumidifiers over desiccant is that they can remove a relatively larger volume of moisture per day. They are therefore particularly useful during the early stage of flood restoration when saturated materials require faster drying. However, extraction rates greatly vary on the air temperature, make and model of the dehumidifier. 

2. Operating Temperature:

The two technologies perform very differently depending on the temperature ranges.  Desiccant dehumidifiers are capable of operating in cold temperature conditions, as the silica gel desiccant still adsorbs moisture regardless of the temperature. On the contrary, refrigerant dehumidifiers experience a drop in water extraction at colder temperatures, as the dew point may be harder to reach and condensation of moisture, in terms of the cold air, is more difficult to achieve.

3. Running Costs:

In general, refrigerator coil dehumidifiers consume less electricity therefore are cheaper to run.

4. Volume:

Refrigerant technology uses compressors which usually make these dehumidifiers slightly louder than desiccant. Since dehumidifiers use mechanical energy and move air, they tend to make noise similar to a typical pedestal fan. While choosing a dehumidifier, make sure that you are informed on the noise it produces (generally in dB i.e.: 38-42dB is typical at 1 metre), however, the latest models produce much less noise than their predecessors so you may find the suitable dehumidifier with noise levels acceptable to you.

5.  Size / weight / manoeuvrability:

Refrigerated coil dehumidifiers are usually heavier as they contain weightier components, and they are often larger in size.  However, the ones we use come with wheels so although these are larger than the desiccants dehumidifiers, they are in some ways easier to move around.  We can also give guidance and advice on the use of each machine.

6. Tank Size:

The dripping water from the dehumidifier is collected in a tank which has to be emptied regularly. The smaller the tank, the more frequently it needs emptying. When the tank is full the dehumidifier automatically switches off. So, it is a good idea to choose a model equipped with discharge pump, that is operated automatically and drain water though attached hoist. 

The Drying Process

Various stages of the drying process, that must be followed, are outlined below. Buildings need to be fully dried before restorative building works can take place. The speed of the drying process depends on the degree and spread of moisture saturation, on what building materials are affected, and also the ambient environmental conditions.

1. Water Pump-Out

It may be necessary to pump out any excess water. 

2. Damp Assessment

Once water pump-out has been completed, or even straight away if water pump-out is not required, the extent of water saturation can be ascertained. This is undertaken with moisture measuring devices. This assessment will inform us on whether any preparatory works are required before the drying program can be set up. This may include invasive works such as cutting access holes in plasterboard walls/ceilings, removing saturated insulation, grinding compounds off concrete floors etc. Any such works will be discussed with the client/insurer before commencing.

3. Cleaning and Stripping Out

Firstly, the silt and debris left by the flood needs to be removed, along with checking gas and electricity supplies and appliances. Stripping out will occur where necessary – likely to include removing damaged, wet furnishings and fittings, as well as hacking off damaged plaster and woodwork, in order to facilitate proper drying out.

4. Disinfecting and Drying Your Property

Disinfecting may be required in advance of drying. This can be assessed with bacterial analysis and mitigated with spray-disinfectant applications.

Drying buildings can take some time as floodwater can penetrate deep into the fabric of properties even if the flooding seems minimal and shallow.

This deep-seated moisture can take a long time to move out through walls and floors, even if the surface appears dry. Full dryness is required so that repair work will be sustainable and damage doesn’t reappear in future.

Drying machines need to be left on for the duration of the period, as any downtime will extend the drying out period. Additional electricity costs incurred should be covered by your insurance. Time required for drying your property can range from a few weeks to many months.

During the initial drying phase, in saturated spaces, a significant volume of water needs to be removed quickly. This is typically best undertaken with refrigerant type dehumidifiers which maintain in the region of 50% relative humidity and can expel moisture that readily evaporates out of building materials.

Deep, structural drying often requires the use of desiccant dehumidifiers to draw moisture out of less porous materials. These dehumidifiers create a very low humidity environment which forces moisture to migrate out of dense building materials.

Heating is also recommended during structural drying. This is because warmer air increases the kinetic energy of water particles within building materials, prompting them to evaporate. Also warmer air can hold more moisture, so heating rooms improves the ability of the air to carry more moisture out of materials.

Fans circulating air also encourage removal of moisture from building materials, by delivering dry air to the affected areas and driving saturated air to the dehumidifiers.

The drying set-up can be adjusted as required, by our technicians, and monitoring of moisture levels will be documented during the drying phase.

5. Repair and Reconstruction Work

A building contractor is likely to be appointed to undertake the repair and reconstruction work. Your insurer is responsible for the work of builders they appoint. If you prefer, you may be able to use your own builder. 

Your insurer can also discuss with you whether you want the repair works to include those which improve resistance and resilience to future flooding. If this doesn’t cost more than the cost of repairing your home to its pre-flood condition then your insurer should not charge for these changes.

Most contents policies will pay for the full cost of replacing damaged items with the equivalent new ones. If the value of your contents is more than the sum insured the settlement of your claim may be reduced to reflect this.

Note: Be Aware of Health Risks

The degree to which caution about health effects need to be taken depends mainly on the type of water contamination and the passage of time from time of flood. Flood water can be either ‘white’, ‘grey’ or ‘black’ water.

While white water is uncontaminated at the time of flood, grey water is wastewater generated from domestic activities such as laundry, showers, dishwashing etc. Black water contains human waste.

Flood water therefore is often contaminated and, even if it appears ‘clean’, may include elements that can cause a range of illness'. Personal hygiene, including washing hands and covering cuts or scratches, is very important during this period in particular. To prevent any unwanted health risks, please wash your hands before preparing food, eating, drinking or smoking.

Due to the damp environmen within a few days mould can form and this can affect the throat, nasal passages and lungs.

Young children, the elderly and those with immune system deficiency should be kept away from properties that have been flooded until they have been passed safe for habitation. Medical advice should be sought immediately if any health concerns are identified.

Extra Equipment


Heaters are used for warming up the air within the surrounding room. It is an object that emits heat or causes another body to achieve a higher temperature. This tool consists of variety of convection heaters that include an electric fan to speed up the airflow. This reduces the thermal resistance between the heating element and the surroundings, allowing heat to be transferred faster. However, heaters operate with a considerable amount of noise caused by the fan and have a moderate risk of an ignition hazard if they happen to make contact with flammable objects. Overall, this type of heater is a good choice for quick heating of enclosed spaces, and combined with dehumidifiers, they significantly accelerate the drying process of buildings.

Deciding the right choice of heaters to use in conjunction with the drying equipment is a very important process. For example, it is clear that any direct-fired type heater, will only contribute moisture to the atmosphere locally and this will be counterproductive to the drying process. Around twice the expected heating needed to heat a dry room is needed to heat a room which needs to be dried out. The additional heat goes into the drying process and the drying time will be reduced significantly by heating. 

Fans / Air movers

Fans are machines which are used to create a flow within the air. A mechanical fan is a machine used to create flow within a fluid, generally gas or air. Such a tool consists of a rotating arrangement of vanes or blades which act on the air.  The rotating assembly of blades and hum are known as a impeller, rotor or runner, and are usually contained within some form of housing or case. Such a case may direct the airflow or increase safety by preventing objects from contracting the fan blades. Most fans are powered by electric motors. Fans produce air flows with high volume and low pressure (although higher than ambient pressure), as opposed to compressors which produce high pressures at a comparatively low volume. 

Using fans in drying buildings is mainly to ensure that humid, stagnant air in the more inaccessible places does not slow the drying rate in those areas, and hence extend the total time needed to return the whole area back to its original dryness. Large diameter fans, for general air movement, are used to ensure that the dryer air, released from the dehumidifiers in the area, can circulate to all parts of the room. These fans have speed control so that noise levels can be kept to a minimum whilst adequate circulation is maintained. More specialist fans are designed to circulate air behind dry lining or under suspended floors and carpets. They therefore reduce the need to remove cladding materials and so save on reinstatement costs. All fans can be run from a domestic 230 volt supply and the power drawn is low enough to permit the use of extension cabling where the local supply may have been isolated. 

Puddle Pump

Designed for pumping water out of flooded cellars, warehouses, foundations, sumps, floodwater from domestic appliances etc.

  • Clearance of water down to within 2mm from the surface.
  • Suitable for pumping clean water only.
  • Variety of pumps available (not necessarily the one shown), some with and some without float switches.
  • Typical flow rates of around 180Litres per minute.
  • Available in 240V.
  • Supplied with discharge hose.

Air Purifier

HEPA (High Efficiency Particulate Air) filter delivers superb degree of air filtration with user-friendly and versatile features. This machine is ideal for handling indoor air quality needs for any job involving sewage, mould or fire damage involving significant amounts of particulates and smelly gasses – a direct result of the damage itself. 

In a water damage restoration environment, the high-velocity airflow needed for drying can stir up particulates that have settled in carpet or on other materials.

  • Numerous air outlets allow multiple air flow directions for targeted drying
  • At 19.9kg, the purifier easy to move.
  • Variable speed outlet provides air output of 562m3 to 713m3 per hour.
  • Dimensions: H 62.5cm, D 46.2cm, W 66.5cm.
  • 1.5 amp power draw.​

Flexible ducting 

For directing dry air into inaccessible places and to exhaust the damp air from desiccant dehumidifiers to outside.


Extension leads 


Can be provided to allow the dehumidifier to operate on a safe 13 amp supply which is remote to the drying area. Circuit protection is recommended in damp environments for safety.



Filters can extend the life of a dehumidifier significantly. 

By using 3M FiltreteTM HAF filters dehumidifiers will run cleaner. They will need to be serviced less often. The chances of it having a longer service life go up. It’s a good investment in your equipment! 

It can be vacuum out  twice before disposing, so it’s like having three filters in one! Make that three superior filters in one.

By using an electrostatic charge, 3M HAF filters are able to operate with twice the efficiency of washable foam. They attract, capture, and retain more particles than traditional filter media!

A 3M HAF filter keeps the coils cleaner so that the dehumidifier is more effective at condensing water from the air. Plus, the filter’s open channel structure has minimal airflow resistance so that the dehumidifier processes' the maximum CFM. With the HAF filter, you get maximum water removal (on very clean coils) and maximum airflow to handle more volume.

A 3M HAF filter includes an antimicrobial agent that prevents mould from growing on its surface. In the warm and humid conditions of water damage, this can keep the filter from becoming a mould colony—which is quite possible with foam or paper filters.

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