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Expansion vessels: Why are they so important?

expansion vessel Flamco flexcon series

Our home's heating systems are placed under enormous duress every day. In tandem with the homeowner's whims, a heating system has to apportion energy, heat and water to: changing the air temperature as well as for use in sinks, showers and baths. We can all point to one important component - the boiler. But other critical constituents of this process fly under the radar. None more so than expansion vessels. To highlight the importance of expansion vessels, we have put together this hopefully illuminating post.

What are expansion vessels?

Expansion vessels consist of a small steel container divided into two parts by a rubber diaphragm. One side of the rubber is filled with air or nitrogen, while the other is filled with water. The steel provides the vessel with a close to impenetrable exterior that won’t fold under hydraulic shock. The rubber diaphragm, on the inside, possesses an extremely low permeability which not only serves to contains pressure loss, but also helps to ward off corrosion.

What is the purpose of an expansion vessel?

Even in a single day, our home can go through many, many heating cycles. When there is demand for hot water, there has to be action on the part of our home. When water is heated up, it expands. And when it expands, your home’s closed water heating system has to be equipped to deal with the added pressure. That is where expansion vessels come in. Thanks to their rubber diaphragms and steel exteriors, they are more than capable of withstanding the effects of both thermal expansion and water hammer, preventing the system from failing or at worst, coming apart completely.
Less commonly, an expansion vessel is also used as a replacement for a continuous pump in a pumped central heating system. Because expansion vessels can be adjusted to maintain a specific pressure level, they can be tweaked to maintain pressure even in the absence of a pump.

Why are expansion vessels so important?

In certain water heating systems, expansion vessels are an absolute necessity. Closed water heating systems, where there is a one way valve present, are vulnerable to increases in pressure. The only way to combat these increases is to introduce an expansion vessel. Without it, you run the risk of damaging not only the water heater, but the plumbing fixtures and the water pipes themselves.

What should you look for in an expansion vessel?

At Pump Sales Direct, we only stock the highest quality products that meet UK regulations, and the same applies to our range of expansion vessels. One of the most reputable and respected manufacturers of expansion vessels is Flamco, of which we are a stockist. Distinguished by their bold red exterior, Flamco pressurisation units are not only instantly recognisable, but amongst the best available today. The importance of ensuring that your expansion vessel matches the specifications of your water heating system exactly cannot be overstated. Fortunately, all of our product descriptions are loaded with detail and should be enough to help you decipher the best product for you. Even if it’s not, you can reach us by email or phone and one of our dedicated team will be more than happy to walk you through it.

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