Proper Duplex Plumbing

michaelcherr

I have a question about the proper way to set up plumbing for a duplex in the following scenario: Tannants pay for gas and electric (two gas meters and elec meters). Landlord pays for water (one water service and meter).

The cold is shared, but the hot water is seperate since tennants pay to heat their portion.

Here is my concern: When cold water is turned on, doesn't it cause a low pressure zone and a little water comes out of the hot water inlet. Is that true? There's no check valve in the standard setup.

In this duplex scenario, would I need check valves on the cold water inlets for the heaters. I know that If I put in a check valve I also would need a vacuum relief valve and an expansion tank.

In my area, only licensed plumbers can work on multi-family dwellings, so I will call a plumber when I do the work, but I just need to know what to ask them to do.
I also need to know as I am studying to be a home inspector, and I'd like to specialize in residential investment inspections.

the_man

in my code, duplexes need completely separate services, which includes water and sewer. there are older places that have only one water line and sewer line, but thats how new construction is supposed to be

michaelcherr

I would guess any new duplex in my area needs seperate services too.
There is a section of town that is mostly large houses from just after the turn of the century, most are converted to 2-4 unit apartments.
Some a illegal conversions, some were converted long enough ago to be legal non-conforming (grandfathered), and some (not many) are zoned multi-family and code compliant.

My duplex for example is zoned as a duplex, but shares sewer and water. The way it's plumbed works, but I'm not a slumlord and I want to make sure it's right (short of getting a seccond water supply and sewer connection)

michaelcherr

So does anybody know the proper way to plumb duplex supply lines if the supply is shared?

michaelcherr

Bump.

AllanJ

If everything works now, you can leave it the way it is.

If you can plumb a single house, it should be a no-brainer to do separate plumbing for each unit in a new duplex or apartment building.

Select locations for separate water meters for each unit. The building feed should first branch and go to these meter locations (individual meters not mandatory while tenants do not pay their own cold water). From the respective meter locations branch off to the respective water heaters and also build on the separate cold water systems.

Water heaters nowadays should each have expansion tank mounted in the cold water feed above. If not and some hot water flows back into the cold line, the amount is too small to make a difference if you did not have separate cold water systems for the apartment house.

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michaelcherr

Just for clarification: A check valve is what stops the water from flowing, a check valve, can cause pressure to build and therefore needs an expansion tank and pressure release valve.

I guess my question is somewhat answered when you said water heaters nowadays should have an expansion tank.

Yes, I have the ability to seperate the water systems, but that would take a ton of work for a house that has relativeley new supply and waste plumbing.

Everything works fine now, I will replace the one water heater in 3-5 yrs. I was just wondering if I could wait till then for expansion tank, check valve and pressure release. (The other tank-upstairs: already has this)