We moved into a new construction home a few months ago. The house has what I believe are 1/2 inch flexible gas lines running from a basement manifold to various appliances (water heater, two different HVAC furnaces, fireplace, dryer, and cooking range).
The builder apparently should have used 3/4 inch line to run to the water heater, which is I believe a 200,000 BTU unit. However, they screwed up on our place and several others, running the same 1/2 inch lines throughout. This caused the water heater to be starved for gas, and it wasn't able to keep up with more than one hot water tap being open.
The distance between the gas manifold in the basement and the water heater is about as great as it could be (water heater lives in a closet on the 4th floor on the opposite side of the house). So obviously ripping out the existing line behind all that sheet rock across 5 stories would be no small feat.
What the builder has done as a solution is to install a t-junction at the 1/2 inch gas line feeding one of the two HVAC heaters (which is on the 3rd floor, directly beneath the water heater). They brought this new 1/2 inch branch up through the floor, and combined it with the existing 1/2 inch line already there. So, the water heater now has effectively a gas line of 1 inch (minus whatever gas might be lost to the in-line HVAC system).
We've tested this setup for the past week, and it does allow us to run multiple hot showers at the same time. I have noticed that if we really stress the system (3 showers running plus kitchen tap with furnaces on), the furnace seems starved for gas and blows room temperature air. However, this would be an extreme usage scenario. We don't run that upstairs furnace much and wouldn't normally have that many taps going.
The builder is wanting to know how this setup is working out. They're banking on our ignorance. What I'm most interested to know is whether there are any safety or regulations compliance issues with the way they have jerry-rigged this setup.
Thank you for reading!