Hi Cristina, You didn’t mention what fuel the water heater uses BUT if it is gas you may have some real problems facing you.
A lot of localities will not allow the use of “gas” and oil into the same chimney for several reasons.
As a boiler inspector (Real licensed plumbers do inspect boilers) we try to keep the oil and gas flue separated UNLESS your using a duel fuel boiler and the chimney is designed for such usage.
One of the main reasons is OIL is considered a WET FUEL and gas being a dry fuel.
When these two fuels are allowed in a chimney not properly designed the DRY gas fuel makes the wet residual from the incomplete combustion of the oil (soot) turn to sulfuric acid and thus corroding out the combined chimney.
Second reason why I personally do not like mixing these fuels is a lot of wannna be plumbers install the gas flue BELOW the oil fired equipment thus allowing the soot to fall back into the gas fired appliance flue and causing spillage ( dangerous gases) and again corroding the gas flue piping exposing everyone to carbon monoxide, NOX and SOX
Harold is correct with a possible over firing of the oil burner and a Bacharach test should be performed by any legitimate plumbing contractor.
What you want to have tested is stack temperature to make SURE you have enough heat to cause an up draft.
You also want a smoke test and an efficiency test, not some stumble bum looking into the flame saying “YUP SURE DO LOOK GOOD TO ME”
If your in an area where the plumbers have no clue TRY contacting your oil company and demand to have these tests performed by someone with a CLASS “A” boiler installers license or the very least a stationary engineer not a country bumpkin plumber.
NFPA 13 and AGA have several proper guide lines and options available.
Most oil companies have some highly qualified folks working for them as unlike self taught plumbers the oil companies have on going training and several top notch schools especially in the New England states.
Most stumble bum plumbers install gas fired appliances and forget them OIL companies on the average take the equipment very seriously they have to if they want to keep their accounts happy.
If you do use a “plumber” don’t be afraid to ask what courses he actually took for HEATING and service and you certainly don’t want someone who only took a correspondence course they found on the back of a match cover.
Good luck and don’t wait to long to have your chimney inspected by a LICENSED Chimney inspector not a clown with a flash light looking up
Harold Large enough chimney is not the only criteria
Making sure the material is compatable with the fuels is just as important.
Hey are we having fun YET?
Sure beating digging fence posts huh.
[Edited by SylvanLMP on 20 March 2001]