How To Prevent Damp and Condensation Build-up

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Published: 19 November 2015


Tony Ellerker, from Blakes M&E Building Services, explains.
One of the most common reasons a building maintenance crew is called out is water damage from leaking air conditioning units. If dark spots have begun appearing on ceilings or walls then you can be sure there is a considerable amount of condensation built up in the system.

Fortunately, there are a few ways you can prevent the damage from ever reaching this stage. But first you need to assess where the leaks might be springing from. Below is a list of common leakage causes and the ways you can ensure they don’t become a major problem.

Overflowing Drain Pans

Disconnected Drain Lines

If left unchecked for too long, the drain line in an AC unit can become clogged with dirt and residue, causing water to collect in the drain pan below it. The drain pan will only retain a certain amount of water, so once this begins to overflow, damp and condensation damage is inevitable.

In order to prevent this build-up from occurring, the drain line needs to be checked regularly. As a rule of thumb, look for excess moisture every time the filter is changed, around once every thirty days. If dirt build-up is present, then it is prudent to blow out the drain line to clear it.

Absence of The P-trap

​A number of AC units run on negative airflow, which means they suck air into the system rather than blowing it through. The negative air pressure prevents water from escaping through the drain line, because of the air rushing in. Often this isn’t a problem until the power is cut off and the built up water begins to pour out again.

The simple solution for most building maintenance companies is to install a P-trap. The unique bend of a P-trap means that water remains trapped in it. The weight of this water then prevents the onrushing air from pushing it back into the vent. In units where the P-trap is not present, the build-up of condensation in the vent can cause major damage when it’s finally released. Taking the time to install this simple component can save you considerably in the long run.
​Sometimes poor installation of AC units can result in PVC fittings coming loose and drain lines disconnecting. With nowhere to go, the water will simply pour out of the unit. Look for damage to these fittings and refix them if possible. However, if the fittings were never cemented properly, you might need to take them off and start again.

Low Refrigerant Charge

​Often an air conditioner that is running low on refrigerant will begin to freeze up during use. Once the power is switched off, this ice will slowly melt, causing water to drip through the ceiling. If this water is allowed to build up it can cause irreversible damage to the plaster.

The same goes for ice crystals in the AC filter. When filters aren’t changed regularly, they become clogged with dirt and restrict the air that flows through them. The lack of air means the filter begins to freeze and the above problems occur. In order to prevent this from happening, the air filter needs to be switched out routinely, especially if there are signs of heavy condensation.
Author Bio: Tony Ellerker has worked in the building services and construction industry for over twenty years. He is currently the director of Blakes M&E Building Services, who provide pre-planned maintenance, reactive repairs and installations of all mechanical and electrical systems throughout London and the South East.