Maybe I should have left this topic until next month to tie in with last October’s spooky showers blog. But my colour emitting shower is still in the post somewhere and I have just spent a few days on our canal boat engaged in an unsuccessful battle to prevent the shower curtain being speckled with black mould spots. That, and the fact that ‘Legionella and showers’ is never far from the headlines in the plumbing press, moved it forward a month.

Of course showers are never going to be really dangerous – after all on this public awareness video they don’t rate a mention – although swimming with piranhas is not recommended. And even though googling ‘dangerous showers’ brings forth an amazing array of dodgy looking shower heads with bare electrical wires hanging round everywhere, none were linked to actual deaths, unlike Legionella outbreaks.

A bit about mould. Moulds organisms are found almost everywhere and can be black, white, orange, green, or purple. Outdoors, they play an important role in nature, breaking down dead leaves, plants and trees. We are exposed to mould spores almost every day and most of us experience no problems. However, some people are allergic to mould and can react in various ways, e.g. hay fever-type symptoms, dermatitis or even asthma attacks.

A bit of building physics. Air holds moisture as a vapour. Warmer air can hold more water vapour than cold air. When saturated warm air hits a cold surface the air cools and the water vapour changes into a liquid; this is what we call condensation. Most homes in the UK are poorly insulated, so external walls are cold, and many still have single glazed windows. When warm moist air from a shower hits one of those surfaces, condensation forms and black mould will grow.

If you prevent condensation, then you will get rid of mould. There are two main ways to do this – better insulation so that there are no longer cold surfaces to cool the air, or more ventilation so that the moisture laden air is taken outside. So, opening a window when showering is a good solution (though I realise this wont be popular with most of you, especially in the winter!) as is a fan in the bathroom that you don’t override. The shorter the shower, the better (hooray!) as less water vapour is formed, and, luckily, having cold showers instead of hot showers doesn’t solve the problem.

There is a third way, and that is to use surfaces that will absorb moisture better than current wall finishes do. Clay plasters have the ability to absorb airborne moisture when the air is saturated and release it when the air is dry, thus regulating moisture content in the room and reducing mould. A friend of mine many years ago experimented with putting a pile of clay bricks in his bathroom. It wasn’t as successful as he’d hoped, but then, to be honest, his bathroom was so cold and damp it wasn’t just the excess moisture from showering he needed to cope with!

So that’s mould, rarely dangerous and quite easily prevented. And Legionella? In my opinion its dangers are vastly overplayed (cue ironic death in later years from exactly this if all the lead and asbestos I ingested on site doesn’t get me first) and I will blog about it soon.

September 2013 – Dangerous showers