Exhaust gas conduction for condensing boiler + gas heater

Hello to the forum

We want to renovate a single-family house. My question: a gas condensing boiler is to be installed for the heating, and the flue pipe is to be routed through an old chimney. I would like to realize the hot water supply for the bathrooms with 2 gas instantaneous water heaters (Jetatherm WRD 18-2g). Is it possible to install the flue gas discharge through the same chimney as the condensing boiler?

Thank you very much

Rajko

I can hardly imagine that 3 exhaust pipes can be accommodated in the chimney. All together on one pipe is not operational and will not be approved by the [Schorni]. Have you ever thought about electric instantaneous water heaters?