Plumbing Supply Piping 101

A home’s water supply piping is a simple system, but it’s mostly hidden behind the walls and in the attic.  When it’s out of sight and out of mind, it can be an unknown for homeowners. That is, until a problem occurs. With modern materials problems are much less likely, but there are still important things to look for during a home inspection.

New Homes:

The modern water piping material of choice is called PEX, which is a shorthand name for cross-linked polyethylene. It’s a plastic material that is easy to install and won’t degrade over time. Any home built in the last five years will have this material, as it’s cheaper and easier to work with than the next best alternatives. It can easily connect to older systems like copper, as seen below.

Older copper piping can be connected to newer PEX material with push-connect fittings.

CPVC looks a lot like the white PVC you’ll see as your sink drainage pipe, but it’s an off-white color with a yellow stripe. Unlike PVC, CPVC is rated for the temperatures needed for a hot water system. Homes that are 10-20 years old will probably have CPVC since it was the most cost effective and easy to work with option at the time.

With these two modern materials, installation deficiencies are what the inspector will be looking for while in the attic or any unfinished areas where the plumbing is visible. Long runs of unsupported piping or poorly fitted connections may be items a home inspector might point out, as they could become a future leak point due to the high stress at the fittings.

A lack of insulation is a common home inspection finding. With two deep freezes in Texas in the past three years, it’s important not to ignore this finding until the next freeze comes around. During the most recent freeze, the City of Houston advised residents not to drip their pipes to prevent overwhelming the city treatment system. Proper insulation is the only way to protect from burst pipes during winter storms.

Older Homes:

Metal water supply pipes are much more common in older homes, because we had cost-effective plastic alternatives. Copper and galvanized steel are the two materials seen in homes more than twenty years old. There’s no rule against using these materials in newer homes, but with the advent of PEX and CPVC, there is no need.

Copper has been a great material for a long time, but it has never been cheap to install. PEX piping is about a third of the cost of copper. A well installed copper system can last the lifetime of a home because it’s not prone to internal corrosion. Like the newer materials, it still needs to be well insulated to avoid cracks and broken fittings during freezing conditions. It needs to be well supported so excess force isn’t put on the soldered joint connections. 

When copper is connected to galvanized steel or another metal material, a proper dielectric fitting needs to be used to avoid galvanic corrosion at the dissimilar metal joint. This type of corrosion is a common finding at the connections above a hot water heater.

Galvanized steel has always been a more affordable alternative to copper but has a crucial limitation: it corrodes internally over time. At best, the corrosion leads to rusty piping limiting the flow of water and periodically plugging faucets and shower heads. At worst, the corrosion leads to thinner piping that leaks, usually at the threaded connections. 

Corrosion will reduce flow and lead to leaks

These unfortunate side effects can take decades to develop and are impossible to predict, which makes it hard to decide when to move on from galvanized steel piping. A home inspection and a new home purchase can be a good time to make a change to a different material, especially if you’re planning to do any other remodeling work to the home.

Several Houston companies specialize in whole home re-piping and advertise a change out of all the materials in one day. One important thing to remember is that getting the piping in the walls changed is necessary to ensure no more potential for corrosion-induced leaks. It is much cheaper and quicker to change out only the accessible attic piping, but the small segments in the walls may still cause problems over time. It may be the best decision to live with the risk of the in-wall piping if no other home repairs are being completed at the time of project, but don’t forget about the small segments during any future projects.

During your home inspection, we’ll identify the type of plumbing supply piping in the home at every accessible location. For newer homes, that is a straightforward task, but a bit more detective work is required for older homes. Knowing what materials you have will help you have confidence in your home buying decision. SMC Home Solutions strives to empower Houston homeowners, one inspection and blog post at a time!