hydrostatic pressure testing

What Is a Hydrostatic Pressure Test in Foundation Repair? 4 Steps

Hydrostatic plumbing tests can be used by plumbing professionals and also by foundation repair professionals. Since you’re not a *professional either one of those things* you might not know what this technical term means. 

Anchor Foundation Repair

Why would you already know unless you just love to go around randomly learning home repair terms for no relevant reason happening in your home? Not that there’s anything wrong with that but we’re gonna go out on a limb and say it’s *probably not very common*.

Anchor Foundation Repair conducts hydrostatic testing on just about every foundation we repair and we have done thousands of them over our 35+ years in business in the Brazos Valley. We can tell you this 4 step process because we do it all the time!

This article will review a quick meaning of hydrostatic plumbing tests and review the 4 step process of how it happens and how it works. We will also go over a few common follow-up questions and concerns about the test. Let’s get not stand still . . . let’s get the information flowing . . . 

What Does Hydrostatic Testing Mean?

Some industry-folk call it a hydrostatic plumbing test, some people call it a hydrostatic pressure test. Both terms are accurate and interchangeable. This type of testing can be done on any type of closed rigid pipe system: like plumbing drain lines. But this test is also used in natural gas lines or other set-ups involving a series of pipes connected together used in science or various engineering applications. 

But we’re gonna talk about how this test is specifically used in home plumbing during the foundation repair process. To be clear, this is for the drain lines carrying water away from your home, not supply lines that bring water to the home.

Let’s go a little Greek here and first define the word hydrostatic. Hydro = water and static = standing still (or not moving). So if you translate that Greek or Latin or whatever, it’s a “standing water test” conducted on the plumbing drain lines under your home.

The main purpose of a hydrostatic plumbing test is to check for breaks in the system, aka leaky pipes. A hydrostatic plumbing test will tell you if the drain line system of your home is *all good* or if there’s a problem that needs repair under your slab where it’s not visible or obvious that something is wrong.

hydrostatic pressure test your plumbing with these tools

4 Steps in the Hydrostatic Plumbing Test Process

Conducting the hydrostatic test is a 4 step process. Before the test can begin, the plumber or foundation repair crew would first ensure that the drain lines are not currently in use. As in, no one is using the washing machine or taking a shower or *anything else* drain lines are used for.

  1. Locate and open up the drain line clean-out
  2. Insert and fill an inflatable test ball to isolate the home drainage system
  3. Fill drain lines to floor level in a tub or shower
  4. Wait and observe the water level for at least 15 minutes

That was a quick step-by-step, but some of that stuff might not make sense so let’s give a bit more detail and explanation.

1. Locate and Open Up the Drain Line Clean-Out

test ball used for hydrostatic plumbing test

Most homes will have a drain line clean-out on the ground outside the home. It looks like a circle in the grass or dirt with a square shape in the middle. It might be white or black plastic PVC. We have included a picture in the main heading in black and here in white. 

When the lid is opened, the pipe goes down vertically, and then it will meet up with another pipe that that is running horizontally. The horizontal pipe is the primary drain line that your home wastewater and sewage runs through to meet up with the municipal sewer system. 

Technically, the pipe is not perfectly horizontal but has a slope to it to help the water drain away from your home and join in with the rest of the sewer system downhill.

2. Insert and Fill the Inflatable Test Ball

The plumbing test ball is sort of like a rubber balloon going flat and has an air valve to fill it up at the right time. The ball is inserted into the clean-out pipe down to where the vertical and horizontal sections meet. The ball is pushed into the horizontal section and then a small air pump is used to inflate the ball all the way until it fills the pipe and blocks off the flow of water.

Inflating the ball blocks off the home’s drainage lines from the rest of the sewer system. This is so that only the home is being tested and not anything beyond the point where the test ball is placed.

3. Fill Drain Lines to Floor Level in a Tub or Shower

fill the drain lines of your home for a hydrostatic pressure test

Now that the home’s drain lines are isolated and blocked off, it’s time to begin filling them up with water. This is done by running one or more water faucets in the house to completely fill up all the drain line pipes for the whole home. 

Normally, home drain lines are not “filled to the brim,” they usually just have water *and other stuff* flowing through them but they are not filled from top to bottom with the wastewater and material. Most of the time it’s more like a water slide with everything flowing along the bottom.

The extra water filling the pipes increases the pressure on the plumbing drain line system and helps expose smaller cracks and flaws in the lines. This is where the “pressure” comes from in hydrostatic pressure testing.

The pipes are filled with water to floor level so that the top of the water line can be seen in a tub or shower drain, or the top of the clean-out in certain situations. Filling to floor level ensures that only the under-slab drain lines are being tested.

4. Wait and Observe the Water Level for at Least 15 Minutes

Once the drain lines are filled up, it’s time to watch and wait. The plumber or repair team is looking to see if the water level drops or stays the same. Waiting for at least 15 minutes or so should be enough time to see if anything is going to happen or the pipes will hold.

If the water level drops from where it started in the visible tub or shower drain, that means that somewhere under the foundation something is leaking and the drain lines are not holding water as they should. If it drops quickly, the crack or hole is larger or there might be more than one. If it drops very slowly, then the crack or compromised area is smaller.

watch to see if the water drains or not in a hydrostatic plumbing test

Can You Test the Plumbing Lines Another Way?

under-slab drain line crack identified by hydrostatic testing

After hearing this step-by-step, you might be wondering if there is any other way to test the drain lines. Like something *higher-tech* because, you know, it’s the 2020s at this point . . . The answer is sure, you could have a camera scope the plumbing. BUT, that camera can miss tiny cracks and you won’t necessarily be able to view any outflow from the pipes.

We honestly think that the hydrostatic pressure test is the most reliable way to check for under-slab leaks. You can LOOK at the drain lines with a camera, but the camera doesn’t TEST the limits of the lines like a hydrostatic test will by putting a bit more pressure on the lines than normally expected.

Can Hydrostatic Testing Cause Damage to My Plumbing?

Has all this talk about pressure got you worried about further damaging the drain lines? We get it, the word *pressure* sounds really dramatic, but it’s not that much pressure. 

No extra pressure is artificially added to the lines other than from the act of filling them up to capacity. The water is not pressurized any further than what normally happens when you fill something up with water. It creates just enough pressure to reveal even the smallest of leaks, but it’s not enough to CAUSE damage that wasn’t already there.

Why Is Hydrostatic Testing Important in Foundation Repair?

Now that you understand the process of how a hydrostatic plumbing test is done, maybe you are wondering a little bit more about why you need it and when it is conducted in the foundation repair process. You’re just full of great questions, aren’t you?

home foundation repair

At Anchor Foundation Repair, we place high importance on hydrostatic testing and have been doing it regularly since 1985. We do it to set up Brazos Valley homeowners with the most stable and secure foundation repairs around and don’t ever want to leave leaks under your home after a repair. That can cause problems for you later, so why would we do that?

Here’s an article that goes into more detail about the whys and whens with hydrostatic plumbing testing in foundation repair.