Thanks, good to know. My tubes pitch a lot and have a only a 90 degree elbow just below the floor and a 45 half way through the run. So they should be easy to clean and check.

A great illustration and animation of an Earth tube (Tube in Tube - flow counterflow) can be found at www.energyreconsidered.com I am familier with this system since an installation in Poland in 2005. To date there has been no reports of any problems due to water, mold or condensation; as this systen works as advertised.