Under-floor Timebomb

As the popularity of under-floor heating increases we are inevitably seeing a larger number of faulty installations. This is the way of the building industry but it needn’t be so. Plumbers are often called in to pipe up under floor heating manifolds to the heating systems after the floor loops have been laid by others.

Because it is trapped, the pipe expansion will take place within the walls of the pipe rather than along it…

Laying pipes into screeded floors might seem like a job for the labourer (beneath plumbers’ dignity) but entrusting this job to someone who doesn’t have the background knowledge is where mistakes are made and hidden until a future date when the pipes fail. The whole system might stand up to a pressure test and be assumed to be fine but when laying heating pipe under screed you need to keep in mind that:

• Plastic pipe expands and contracts as it heats and cools.
• This expansion doesn’t cease when it is buried in sand and cement.

Because it is trapped, the pipe expansion will take place within the walls of the pipe rather than along it but where the pipe leaves the cement screed and enters free air is a critical point. Suddenly it is able to expand and contract freely along its length but the point of transition is susceptible to abrasion. It must be sleeved at this point either with plastic conduit or pipe insulation to prevent this happening. If this isn’t done there is a risk of leaks occurring. The other vulnerable point in under screed pipes is the thresholds between rooms. The screeds between rooms always crack at this point and this is a wholly good thing because it allows each room to act independently. It does however mean that the pipe at that point will move minutely and, again, abrasion can wear the pipes. This will also happen where pipes go through walls.

Pipe failure could be 10 or 15 years from now, and whilst plumbers and builders will be free of their warranty obligations by then, it is not a long time in the life of a building, or perhaps I am out of step by thinking that pipe which is guaranteed for anything from 25 to 50 years ought to actually last that long in a building as well as a laboratory.