Results of experimental and calculational studying of the stressed-and-strained condition of a tube bundle of a horizontal heating-network water heater under different regimes of operation are presented. How a change in its vibration characteristics effects the stressed-and-strained condition of a tube system is shown and the static strength of the rolled junctions of the tubes with tube desks is assessed. Copyright © 2005 by MAIK "Nauka / Interperiodica" (Russia).