Water Pressure/Plumbing Question

[Adam Belasco]

Hi BP,

Thanks in advance for any help!

Background: I recently purchased a 5,400sqft duplex that was running on one hot water heater which was located in the basement. The property has three floors plus a basement so naturally I'm rehabbing this property to be a triplex (each floor its own unit). Each of the three units will have their own hot water heater located in a utility closet in their unit plus a dishwasher, washing macine, and then one bathroom per unit, with the exception of the first floor which will have 2 full baths (total 4 full baths in property). The property will also have a sprinkler system installed throughout.

Question: Currently we have a 3/4" line coming into the house in the basement from the main line which we're then going to expand to 1". Is that enough to support the 4 full bathrooms throughout the house, one hot water heater in each of the 3 units, plus dishwasher and washing machine in each unit? I was told that it'll be fine, but I'm wondering if I need to spend the extra money, permitting, etc to have the line from the main be changed to a 1" and then tie into a 1 1/4" line in the house?

[Matt Devincenzo]

Plumbing sizing is based on Fixture Unit count, so what is you FU count? This can or cannot include fire sprinklers depending on the set up. It also depends on the local agencies perspective on meter sizing based on the FU count. My guess based on similar projects in my area is you'll be well over the FU for a 3/4" and will need to upsize to a 1" meter. From there the backside 1"-1.5" is a choice for you to determine if you need the additional size or not. Again the plumbing guidance gives a FU and total height table to determine what size line is required by code. 

Are you permitting the rest of the three unit conversion, because if so then it seems this would have come up as part of the mechanical plan check? 

[Julien J.]

Sounds like a question for a licensed plumber. There are a few variables at play and you are likely to have to pull permits and follow current codes.