Plumbing Issues That Can Make or Break a Flip

Plumbing is one of the most expensive systems to repair or replace, and hidden plumbing issues are a leading cause of flip budget overruns. Thorough plumbing evaluation during due diligence is non-negotiable.

Supply line material matters. Copper pipes are the gold standard — durable, long-lasting, and well-regarded by buyers and inspectors. PEX (cross-linked polyethylene) is the modern standard for new construction and remodeling — it's flexible, freeze-resistant, and less expensive than copper. Galvanized steel pipes (common in pre-1960s homes) corrode internally, restricting water flow and eventually leaking. Full replacement costs $4,000–$10,000. Polybutylene pipes (common in the 1980s) are prone to failure and should be replaced ($3,000–$8,000).

Drain lines carry even more risk. Cast iron drain lines in pre-1970s homes corrode and develop belly sections (low points where waste accumulates). A sewer scope ($150–$300) reveals the condition before you buy. Full drain line replacement costs $5,000–$15,000 for interior lines and $3,000–$10,000 for the main sewer line to the street.

Sewer lateral condition is critical. The line from the house to the city main is the property owner's responsibility. Tree root intrusion, bellies, offsets, and collapses all require repair or replacement. Trenchless technology (pipe lining or pipe bursting) costs $4,000–$12,000 and avoids the need to excavate the yard.

Water heater replacement is a common line item: $1,000–$2,000 for a standard tank, $3,000–$5,000 for a tankless unit. If the existing water heater is less than 5 years old and working properly, leave it.

During property walkthroughs, check water pressure at multiple fixtures, look for water stains on ceilings and walls, inspect under all sinks for leaks, check the water heater for corrosion and age, and note the pipe material visible in the basement or crawl space. Always order a sewer scope on pre-1980 properties.