I have an 10 year old Rheem forced hot water heater I am going to add a second zone with taco zone valves I am familier with hooking up the zone vavles but how about the heating system It just has one thermastat hooked up now do I have to add a low voltage to the circuit or can it be run off the present system ty

It really depends upon what you have now.
You will need
Thermostat
Zone valve
Zone relay with built in 24 volt zone power supply.

Depending upon the system you might have to add a additional circulating pump or increase the capacity of the old pump by replacing it with new.

HVAC companys design what the system needs before they do the job. My recommendation is that you read up on hydronics so you can make sure your design will work and be compatible with your components you choose to use.

Design work is usually carried out after a on site visit to the job site so the system can be seen and to figure if the system boiler will actually carry the additional load. Once that calculations is made then and only then is the second zone considered.

There is more to adding a zone that some pipe and controls.