Documenting the existing plumbing systems on a site visit can be challenging because much of the systems will not be readily visible. However, the more information that is well documented on plan and through photos, the more cost effective and clear the design drawings will be. The primary utilities that need to be documented are:
- Domestic Water
- Sanitary Sewer
- Grease Interceptor
- Natural Gas
- Water Heater
- Fire / Sprinkler Service
Domestic Water
In most cases a building will have an exterior water meter box installed flush with hardscape or landscape. Keep in mind that it can be remote from the building, such as by the street.
Lift the cover off the box, and you will likely find a meter partially submerged in water and/or dirt. A thorough inspection involves digging into this to measure the diameter of the pipe. Messy, but domestic water service line size is important information and the face of the meter gives no indication as to size.
The water service continues from the meter into the building, so if you can find the entrance riser, the line size may also be measured here.
A building with multiple tenants can have submeters for individual billing. These will either be located in an accessible location for viewing,
…or provided with a remote reader at a more accessible location. The picture below shows a meter up at the roof structure, but the wire indicates there is an associated remote reader (also pictured).
Backflow preventers and pressure regulating valves are two accessories to keep an eye out for and document when identified. Backflow preventers are required to protect the city water supply from the potential contaminants generated in the building being served.
Pressure regulating valves are an indication of good water pressure at the building. While they may still be installed at lower pressures, they are required on any water service that exceeds 80psi.
Sanitary Sewer
Since you can’t see the sanitary piping below a building’s slab, it is important to document as much as possible to have a sense where the underground piping may be. Existing plumbing fixtures should be documented by both photos and locations indicated on a floorplan. The below picture doesn’t look like much, but it is very helpful if its location is shown on plan since it indicates existing sanitary piping below slab.
Floor cleanouts are access points into the drainage system and are provided in long runs, any 90 degree change of direction of piping, and sometimes when a sanitary main exits the building. These are very important to identify and document on a floor plan.
Sewer manholes located at the exterior of the building are important to note as well. These are a helpful in determining where a sanitary main may be exiting the building.
Manhole picture with satellite location:
Sanitary sewer systems are vented to the exterior through the roof, and are usually PVC. Identity size and location of these VTRs on plan. This is helpful information to note on design plans to avoid calling for new roof penetrations.
Grease Interceptor
Take note of any grease interceptor currently installed. Interceptors interior to the building are small, of steel construction, and are located either on the floor or recessed into the floor.
Exterior interceptors are large, precast concrete structures that are typically identified by two manholes in line with one another. These manholes may or may not be cast with the word ‘Grease.’ There is no way to identify the capacity of these interceptors by visual inspection.
Natural Gas
Natural gas service equipment will always be on the exterior of the building. Gas is delivered at high pressure to the meter bank, and is reduced in pressure upstream of the gas meters. A 7”w.c. (0.25psi) delivery pressure is most typical, but 2 psi systems are often installed to reduce the size of the distribution piping. A 2psi system should be labeled with stickers indicating this pressure, but this is not always the case.
Natural gas supply with no current meter installation (still important to document):
If pressure regulators are provided at rooftop units, their nameplates will often indicate inlet pressure.
Water Heating
Identify any water heaters that may be existing. Locate the water heater on plan, and take two pictures – one overall photo and a separate, close up photo of the nameplate. The nameplate will indicate volume and either kw input (electric water heater) or BTU input (gas fired water heater).
Fire protection
Verify if the existing building has sprinklers. An existing sprinkler system will require us to account for sprinkler modifications with the renovations. If the building is sprinkled, locate the sprinkler riser and take photos. Take note of the delivery pressure. Since the fire water is fed from the same main as domestic water, noting this pressure provides good information for the domestic water system design as well.
