Replumbing the Historic Stimson-Green Mansion
We are currently working on an interesting project at the Stimson-Green Mansion in the First Hill neighborhood of Seattle. Built in 1901, the mansion is a designated Seattle Landmark, is on the Washington Heritage Register, and is on the National Register of Historic Places. Although less spectacular than restoring a forgotten gem, our replumbing project at the mansion will bring safe water, energy efficiency, and increased flow to the historic structure for the next 100 years.
The existing, original, pipes are made of lead and cast iron and have been rusting into the water coming out of the fixtures. Our project scope is to replace the hot and cold water supply lines throughout the building with modern cross-linked polyethylene (PEX) products while reusing the original fixtures. The project is taking place while the building is occupied, requiring us to keep water live at all times and keep shut-downs to a minimum of 2 hours for the whole project. We are phasing the work, beginning with the bathrooms.
We face several challenges with the project, most notably the absence of “as-built” documentation showing us where the existing plumbing is located within the walls of the mansion. We also need to complete our work in the least invasive manner possible while preserving the historic period features of the building including the woodwork and ornate plastered ceilings while at the same time removing and reinstalling historic tile bathroom floors for access. If we discover lead paint and/or asbestos, we will have to take the time to abate it and then continue our work. And all of our work needs to be completed within a short timeframe.
Caution is needed all along the way with a project of this nature starting with doing our homework and performing exploratory work to make sure no hidden surprises will pop up. These could include hidden obstacles in the path of the new lines or discovery of lead paint and/or asbestos, which would have a huge impact on our schedule and budget should this not be found at the exploratory stage. In planning, we decided to run the new plumbing down from the attic through the walls instead of running it under the floors which would have required extensive removal of old floor treatments.
We start by protecting all areas of work using carpet masks, hardboard wall protection in hallways and doorways, and plastic zipper doors to the areas of work, noting any pre-existing damage present. Next we begin to carefully deconstruct flooring and walls to access the existing plumbing system and remove it, taking care to not harm the original fixtures that will be put back in place. We are extremely selective as to where we are accessing these pipes as to keep the building’s historic features intact.
Next we open the walls that we identified as the new supply line route in the exploratory and planning stage. Again, we take great care to keep the building clean by utilizing two HEPA air scrubbers and a HEPA vacuum on all stages of this work. Our plumbing subcontractor then runs the new PEX pipes, now able to make gradual curves instead of the hard 90 degree corners of the original system, and connects to the historic fixtures that are being reused. When complete we do a final test for soundness then have the entire system inspected by the Seattle & King County Department of Public Health.
The last step in the process is to replace the wall and floor areas that were opened for access. This will involve patching walls, pouring a new concrete pad for the bathroom floors, retiling the bathroom floors, and replacing any floorboards that were removed.
In the end the building looks just like it always has, but the efficiency of the pipes has increased in terms of keeping hot water hot as well as having better resistance to freezing, the pipes are more leak resistant, and they provide an increased flow rate due to fewer pipe connections.