Condensate-Harvesting Condensation

Harvesting Condensation

Condensate appears when airborne water vapour (which we sometimes refer to as humidity) touches a cooler surface. The water vapour (gaseous water) changes back into its liquid form. This liquid is known as ‘condensate’. The process by which the vaporised water changes back into water is called ‘condensation’, although nowadays, most of us use the terms ‘condensate’, and ‘condensation, interchangeably. KCS Advice however strives to get things exactly right.

Harvesting Condensate is part of the water efficiency approach which we promote and which includes Rainwater Harvesting. We already feature advice, elsewhere on ‘condensation’ but readers may be interested in the more scientific and technical side of what ‘condensate’ itself is and the water efficiency opportunities which it condensate offers.  And coping with ‘condensate’, plays a much bigger part in the building and construction industry and in life in general than we may suppose.. The ‘condensate’ which accumulates on a cold beer glass on a humid day is mostly considered by us to be an inconvenience. But the process of turning water into vapour and the process by which it condensates back into liquid is not merely an inconvenience for drinkers, DIY enthusiasts and householders to overcome. Condensation is essential to life on Earth.

Domestic Condensate Harvesting


Harvesting domestic condensate

The condensate which collects on large installations such as refrigeration and air conditioning plants is a possible source of significant amounts of usable water and can be harvested. Refrigeration and air conditioning works with a closed loop process and by compressing and decompressing a refrigerant which absorbs the heat. In the process condensate must formand the water can be used for various purposes. In an air conditioning system the air is cooled by the heat exchanger coils and the water vapour in the air turns into condensate.

This condensate water must then be taken away otherwise water damage to the air conditioning system or the building itself might result. Usually air conditioning condensate drains off into a drip pan following which a hose disposes of the condensate into the drains. At least 5 gallons of condensate a day can be realistically harvested in a home and anything up to 20 gallons is a achievable.

The amount of condensate which can be harvested from a social club where as many as several hundred people, are drinking for several hours in a warm confined room is enormous as is the amount of condensate which can be harvested in a gym, or a heated indoor swimming pool, The condensate would be more than enough to water trees in the garden and make a significant dent in the building’s water bills. Even a small dehumidifier in the basement of a house will harvest enough condensate to water the pot plants and the window boxes. It’s a sad fact that all of the necessary condensate harvesting equipment is already in place in many buildings. It’s just a question of collecting the condensate and using it. To date in the world of unmetered water more thought has been given to ways of disposing of condensate that has been given to harvesting it

Harvesting Condensate on an Industrial Scale

commercial grey water   clarifying system

commercial grey water clarifying system

Non residential buildings are also good prospects for use and collection of condensate water. Anywhere which has air conditioning or refrigeration already installed has the condensate harvesting equipment in place. As with residential buildings clean condensate water is routinely poured down the drains whilst the occupants pay for metered water from the mains for uses to which the wasted water itself could easily have been applied. Typically between four and nine gallons of condensate water a day is available from every 1000 square feet of office space serviced by air conditioning.  Even a modest office building can provide as much as 20.000 gallons of condensate water a year.

Although condensate water from air conditioning equipment is as pure as distilled water it must never be used for human consumption. There is a slight risk that condensate water from air conditioning might contain heavy metals from having been in contact with the cooling coils or the soldered joints around the coil.. It should also be noted that the absence of minerals in condensate water makes it more corrosive to metals than even tap water. But condensate’s low mineral content and absence of chlorine and other sanitizers makes it perfect for irrigation purposes. In a human environment condensate takes its place with harvested rainwater. Condensate water however is much safer to drink in small quantities than say harvested rainwater because it does not have the biological pollutants such a bird faeces which can be harmful in small amounts and which are present in rainwater. No condensate water is likely to have such levels of lead or other heavy metals in it that it one glass would be harmful but a glass of water which has been exposed to bird faeces might well be. The fact is however, that although some domestically available filters will remove heavy metals these substances are not removed by boiling or by any other domestically available sanitation process Drinking or cooking condensate water should be avoided and is in any event unnecessary. But these facts do not diminish the value of harvesting condensate water in the home or elsewhere. The proportion of water we drink is very small compared with the amount we use for other purposes, and all of the water we can harvest can be used with no risk at all for purposes other than direct consumption.

In non residential installations the simplest use for condensate is in the cooling tower itself. Cooling towers generally have to dispose of much of their water several times a day owing to the build up of mineral deposits and the water to replenish it has to be from the metered supply. Condensate contains none of the dissolved solids which cause this build up and the need for frequent regular disposal, so not only is the water a free alternative supply but condensate lasts longer without having to be changed. And there are any number, of other commercial and industrial uses for it. Any system which requires water can be serviced by harvested condensate. Over time condensate will be used more and more as more premises are water metered in the UK and water efficiency moves higher up the agenda. In future articles KCS will be explaining the workings of condensate pumps, drains and soakaways.

The oil and gas industry is a ready source of condensate water. Condensate water is a by product of the low and high pressure separators but has to be processed to remove hydrogen sulphide from it. There is no reason that the condensate can’t be used for the same purposes as the water which comes from air conditioning. But Oil, napthan and gas have their own distinctive condensate which forms from the very light hydrocarbons used in refining.  This condensate is recovered from gas reserves by cooling the wells to lower the gas temperature to below its ‘hydrocarbon dew point’. The condensate harvested is similar in characteristics to very light crude oil and can be used in the petrochemical industry and for oil refining feedstock.