Sewer Lateral Water Pressure Test

The water/pressure test is the most important part of the inspection that requires a skilled and knowledgeable Sewer Master to perform the test correctly. If not performed and administered correctly could result in failed water/pressure inspection test by the City and EBMUD inspector and will request a full sewer replacement in order to pass.

Existing Private Sewer Laterals – 3 types of pipe material

VCP (Vitrified Clay Pipe) – Pipe made from clay that has been subjected to vitrification, a process which fuses the clay particles to a very hard, inert, glass-like state. VCP is commonly used in sewer gravity collection mains because of its reasonable price and resistance to almost all domestic and industrial sewage, particularly the sulfuric acid that is generated by hydrogen sulfide, a common component of sewage.

VCP is typical for a lot of homes built in the 1950’s in the Bay Area. Unfortunately VCP pipes have cracks in it which leads to weed intrusion and clogs the systems which results to slow drainage from the sink, toilet, bathtub and washing machine waste line. Existing private sewer lateral lines built with VCP usually fail the initial water pressure test and will need a full trenchless sewer lateral replacement. Sewer Master’s video inspection process identifies the material of pipe during our site investigation.

Cast-iron – Pipe which has had historic use as a pressure pipe for transmission of water, gas and sewage, and as a water drainage pipe during the 19th and 20th centuries. It comprises predominantly a gray cast iron tube and was frequently used uncoated, although later coatings and linings reduced corrosion and improve hydraulics. Cast iron pipe was superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970s and 1980s. Little cast iron pipe is currently manufactured

Cast-Iron pipe comes in 10’ lengths and is connected by rubber couplings and tightened by metal bands to ensure a tight connection. The cast-iron pipe is sometimes cut to fit certain sections of the sewer line, which is common but if not cut correctly could results in a hairline fracture to the pipe. Water/pressure testing of cast-iron is always a challenge because when the cast-iron was originally installed no water/pressure testing was required. Problems associated with water/pressure testing cast-iron is that the original couplings located underground could fail and to tighten, repair failed couplings connections would cost more and it would be more cost efficient for a full trenchless sewer lateral replacement.

SDR Pipe – Pipe manufacturers use the “Standard Dimension Ratio” – SDR – method of rating pressure piping. The SDR is the ratio of pipe diameter to wall thickness and the SDR can be expressed as
SDR = D / s (1)
where D = pipe outside diameter (mm)
s = pipe wall thickness (mm)

A SDR 11 means that the outside diameter – D – of the pipe is eleven times the thickness – s – of the wall. with a high SDR ratio the pipe wall is thin compared to the pipe diameter with a low SDR ratio the pipe wall is thick compared to the pipe diameter.

As a consequence a high SDR pipe has a low-pressure rating and low SDR pipe has a high-pressure rating.

SDR pipe usually means that the city had the lower sewer lateral replaced 15 to 20 years ago from the curb side to the city main. The upper sewer lateral, which runs from the perimeter of the house to the city curbside, could be built with either VCP or cast-iron pipe.

SDR pipe installed from the curbside to the city sewer main usually passes the initial water/pressure test and all that is needs to be water/pressure tests is the upper private sewer lateral.

dual water pressure test