Tonio sputnik

Hi All, I have some experience in this as I already setup and installed my own wood-burning Fireplace in our Penthouse and built an additional duplex floor but this time round I wish to install a pellet stove. I already bought the stove and the pipes so now for the real thing. The structure of the building construction is limestone slabs and marble flooring so there is no issue of anything catching fire. As you all know, a pellet stove shoots out of the back, through the wall into a tee fitting. For the outside I have double walled tubes all in stainless steel. The top of the tee extends the flue gases up the whole building and high enough according to the regulations and ends with the appropriate cap on top. There is no difficulty till here. The tee bottom part is supposed to have a removable cap which can enable you to open and remove ash. Now my problem is that behind the stove where this tee is, there is no floor but a sheer drop of 21meters high so opening this cap to remove any ash is impossible. I have thought of extending the tee by an additional 2 meters down and fit an inspection tee which ends adjacent to a window on the lower floor which enables me to open the inspection plug and remove any ash. my question is if this extension down would present any problem or be illegal in any way? I am more concerned if this will casue any problems with the evacuation of the smoke. my head tells me that it is not a problem but I have never seen anything like in any flue design. Anyone can put the pros and cons of this please? Many thanks in advance.