4 ways to perform a joint test: A how-to guide
Last month we discussed why consistent joint testing is a crucial and often overlooked step. This month, let's get practical and outline some common ways you can joint test, break down the benefits and drawbacks of each, and summarize the steps involved. [LINK]
To start, there are essentially 4 different ways to joint test.
- Hydrostatic Testing
- Internal Joint Testing
- Traditional External Joint Testing
- Straub External Joint Testing
Each of the different styles of testing have unique benefits and drawbacks. They also apply differently depending on the size, material and shape of the pipe being tested.
Regardless of testing method, you're going to want to make sure you've got two good QC pipes and a good fit on the gasket before you begin testing, otherwise you're going to waste a lot of time, money and effort.
Hydrostatic testing is straightforward and one of the most common methods of testing. Home the pipe, seal the ends with pipe plugs, tighten by either ratcheting or inflating the ends, and then restrain and reinforce the pipe with planks or come-along winches.
Once you've done all that, fill the pipe, making sure to carefully bleed the air as you do so. This process can take a long time — a really long time. You'll also need a lot of water on hand. Finally, it's limited to 12'-18' pipe, so keep that in mind.
Internal joint testing (IJT)
IJT offers a lot of benefits over hydrostatic, if you're willing to foot the bill and have the resources on hand to pull it off. Common brands like Cherne or PlugCo offer equipment that allows a much more focused test. IJT is only really feasible on pipes and culverts that measure 21' or more. Consider that before choosing this method.
First, a small pair of bladders is rolled into place inside the testing area. The pipe is restrained to keep pressure safe and stable. Air is used to fill the bladder until it has an adequate seal, and then water is pumped in between the bladders to test. IJT is a great option, but the cost can be off-putting. You also need to have both air and water on site, which can be a hassle for more remote installations.
External joint testing (EJT)
EJT is a tried and true method of joint testing, but as anyone who's done EJT can tell you, it can be a real headache. EJT involves homing the pipe, restraining it, then closing the exhaust valve, drilling holes through the bell, injecting water between the primary and secondary gasket, and pressurizing.
The benefits of EJT are that it's usable on any size of pipe including box culverts, and you're likely to get a far more realistic reading with external testing over internal. The negatives are that you're drilling two holes in your pipe: one for the exhaust port, one for the water line. These holes require a good epoxy nipple to seal tight as well, even if green. The drilling, homing, sealing, epoxying and pressurizing can be a destructive and exhausting process, but the results almost make up for it.
Straub testing is an external joint testing technique that takes all the benefits of Cherne and Plugco internal testing and applies it to the more realistic readings of external tests. Straub testing is still pretty new and somewhat limited to medium-to-large round straight wall pipe only. It also comes with a higher price tag than a standard EJT might, but the costs are generally balanced out by the time and effort saved.
With the Straub, there's no drilling and no need for a secondary gasket either, limiting the risk of fractures or cracks. Step 1: home the pipe, then restrain the pipe, strap the Straub over the bell, tighten with a ratchet (no air needed), fill and pressurize.
The ease of use, time saved and enhanced accuracy of the results compared to realistic conditions make the Straub test a great choice, even if the limitations of pipe size mean it's only good for specific types of pipe.
Testing is an important step in the installation process, but so much of it seems daunting or costly. Hopefully this overview helps encourage you to test more regularly, more carefully, and more accurately in the future. Heck, why not make it a new year's resolution?