Ask the Agents #23: What is a hydrostatic test?

Question: What is a hydrostatic test? Do I need one?

Answer: One of the most important systems in any home is the plumbing. Incoming fresh water is essential, of course. But just as important is the egress of used water from washing machines, bathtubs, kitchen sinks and, of course, toilets. No one wants to buy a house only to find out a month later that there’s a serious problem with the plumbing.

When you have a contract to buy a house, the first thing to do is arrange for a thorough inspection of all structural and mechanical systems. In the course of the inspection, the inspector or your real estate agent may suggest also having a hydrostatic test. Obvious clues include cracks in the foundation, discolored water pipes, standing water near the house, mature trees sending roots under the house, damp flooring or a smelly spot in the yard. Even if none of these things is present, you may still want to have the test done, especially if it’s an older home you are buying. The test can be performed on plumbing systems on a slab foundation as well as pier-and-beam.

What is a hydrostatic test? It is, essentially, a pressure test that can pinpoint any leaks in the house’s plumbing and has been in use since the 1970s. The test is performed by putting an inflatable rubber ball in the cleanout outside the home, inflating the ball to plug the sewer line. A stand-up shower drain or toilet (removed to expose the floor flange) gives the inspector a level observation point, and the house’s first-floor plumbing system is filled with water via a sink or bathtub faucet. The water level is then monitored for about 20 minutes to see whether the water level drops or stays level. If the water level drops (or if the water refuses to fill up to the home’s slab level), chances are there is a leak in the system.

Note that only a licensed plumber may perform a hydrostatic test on a system within a home. Some inspectors are also licensed as plumbers, and they may perform the test. The cost depends on how extensive the plumbing system is. In River Oaks a hydrostatic test typically ranges from $400 to $800.

Some homeowners are leery of hydrostatic tests because they have heard that the tests can cause damage to their pipes. In fact, they very rarely do. There is no unusual pressure on the plumbing system; it’s being tested the same passive way it was meant to be used. Some damages have been reported with the toilet removal – e.g. chipped floor tile – and reinstallation, but that is rare.

Nevertheless, the Texas Real Estate Commission (TREC) has a promulgated “Addendum for Authorizing Hydrostatic Testing.” This form asks the buyer and seller to agree to the test, names the party responsible for payment (most often the buyer) and sets a cap on any monetary damages.

A hydrostatic test is the only way to find out if there are any leaks or damage in sewer pipes. However, the test determines only whether or not there is a leak, but not where the leak is located. If the hydrostatic test indicates a leaky pipe, the next step would be to bring in a camera snake to pinpoint the location and then make the needed repair. A camera inspection is also well suited for locating clogs.