Thread: Drain test

Do any of you have experience with a hydrostatic drain test? I picture it similar to a shower pan test using a stopper in the drain and filling up the pipe. Seems like a high potential for a false leak if the stopper doesn't fit perfectly. Also wondering about how often an old house with cast iron pipes would pass this type of test. They don't do them where I live, but my cousin in Houston is asking about it for his house.

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• Test

As part of a code inspection (AHJ) all the time, or litigation (not permitted to leak) a few times.

A plumber's test ball is inserted either outside the building at the clean out (for a full system test, 3 floors is the likely maximum for this because of test ball failure/leakage/blow out due to the head pressure, or first phase of a phased install test); or the test ball is inserted into test tees installed for the purpose of testing the next partial phased install (typically 3 story and more buildings are phasedoing install and those sections are tested, then on to the next phase of the install).

The test ball is inflated in the clean out or test tee, typical failure is due to under inflation and either water leaks past the test ball or the test ball is pushed down the pipe, occasionally a test ball will fail (explode) due to to much pressure (air or water).

The test is made with a minimum of 5 feet of head above the highest fitting being tested - or filled to overflow the vent on a full system test. The code went to 10 feet of head, but I think it changed (or is changing) back to 5 feet of head.

The test needs to have no visible evidence of leaks for 15 minutes.

The part many inspectors and contractors fail to test is everything overhead, and when tested, those are where the leaks are typically found. Need to fill the system to overflow the vent through the roof or at least 5 feet above the highest fitting.

If an old system is tested and doesn't pass ... that system needs repair or replacement.

Very common here for under slab cast iron pipes, due to the extremely expansive clay soils here.
This will be a modified test to the lowest opening (i.e. toilet flange at first floor) isolating the under slab pipes only. It is very common to fail this test even with the lower head pressure.

Here, a plumber does the test and separate permission is needed from the seller if the test is inside a standard sales contract using the State written contract.

Having seen so many failures, I recommend testing on any slab foundation home with cast iron and any home that has had the foundation lifted/repaired.

A video inspection would be the logical follow up to a failed hydrostatic test to find where the leak is and further examination of the condition of the pipe system.

Originally Posted by Jim Luttrall

Very common here for under slab cast iron pipes, due to the extremely expansive clay soils here.
This will be a modified test to the lowest opening (i.e. toilet flange at first floor) isolating the under slab pipes only. It is very common to fail this test even with the lower head pressure.

Here, a plumber does the test and separate permission is needed from the seller if the test is inside a standard sales contract using the State written contract.

Having seen so many failures, I recommend testing on any slab foundation home with cast iron and any home that has had the foundation lifted/repaired.

A video inspection would be the logical follow up to a failed hydrostatic test to find where the leak is and further examination of the condition of the pipe system.

That's pretty much the scenario. They did do a video scan, or there is one ordered. I was just curious if there is any idea of how many, if any, houses with cast iron pass the test. I can see with plastic it not being an issue. I guess that is information we don't have.

Originally Posted by Jim Robinson

I was just curious if there is any idea of how many, if any, houses with cast iron pass the test.

I don't know how many can, do, or will pass the test, but ... I know how many should be able to pass the test (regardless of the material used for the DWV) - all of them.

Originally Posted by Jim Robinson

That's pretty much the scenario. They did do a video scan, or there is one ordered. I was just curious if there is any idea of how many, if any, houses with cast iron pass the test. I can see with plastic it not being an issue. I guess that is information we don't have.

Purely anecdotal but what I see is at least half of the houses I have contact with in this scenario fail. Most of these houses are at least 50 years old and are likely to have foundation movement. We have very expansive soils combined with wild extremes on ground moisture which translates to more movement than cast iron can handle. Going from total saturation of the soil around the house during the rainy season to totally desiccated soil during frequent drought conditions make for foundation and pipe stresses beyond belief. Get a small plumbing leak and the foundation heaves and buckles around the leak. Around here sewer testing is money well spent.