A common problem in manholes is leaks around pipe penetrations. Normally, a gasket seal in installed around the pipe during construction. Sometimes, however, the seal is installed incorrectly or never installed at all. Even if the seal was installed correctly, it can break if the structure settles, or it can fail from repeated pressure fluctuations from a rising and lowering groundwater level.
It’s costly and sometimes nearly impossible to install a new gasket seal, so often the best solution is to use Prime-Flex Hydro Gel SX, a fast curing injectable polyurethane grout, to form a new gasket "in-place." Here’s how it’s done.
First, you will need to drill a hole through the side wall of the manhole into the source of the leak. The hole should be drilled six to thirty-six inches from the leak—closer for slow leaks, further away for high volume leaks. You will know that you have found the source if water begins to flow through the drilled hole.
If the hole is dry, drill again until you hit water flow. If you are repairing a high pressure or high volume leak, the next step is to slow the water flow. The newly drilled hole will reduce some of the water pressure, but you will also need to reduce the volume of water flowing through the joint. For this, use Oakum, a dry, fibrous, rope-like material. The Oakum can be pushed into the gaps around the mainline pipe using a screwdriver. When the water flow around the mainline pipe is slowed, the Prime-Flex Hydro Gel can be injected.
For small leaks, many contractors prefer to use a manual, double barrel caulk gun and a Hydro Gel "Quick Mix" dual cartridge. One cartridge contains Hydro Gel; the other is filled with water and Gel Reinforcing Agent. The contents of the two cartridges are pumped through a spiral mixing tube that is designed to be pushed through a 3/8 inch drilled hole and is long enough to extend to the outside of a manhole structure.
For larger leaks, a pumping system works best. Prime Resins offers a line of air operated pumps designed to deliver Hydro Gel SX and the water/Gel Reinforcing Agent at variable ratios. The material is injected through the drilled hole by using a stainless steel nozzle, or "wall stinger," that is pushed into the hole.
As the Hydro Gel SX is injected, it flows behind the structure where it mixes with groundwater and flows to the source of the leak. The fast setting Hydro Gel forms a tough polyurethane gasket in the joint, and a waterproof curtain around the outside of the pipe. If Oakum was used to slow the water leak, the Hydro Gel SX will be absorbed into the Oakum and form an Oakum-reinforced seal. The Hydro Gel SX that flows into the surrounding soil will also fill voids and stabilize the soil.
Hydro Gel SX bonds with concrete and retains its strength and flexibility for many years. Often the Hydro Gel SX seal allows for more movement and withstands external pressure better than the originally installed seal. That means that a simple, quick, and cost-effective mainline pipe joint repair with Hydro Gel can last for years.
To learn more about Hydro Gel and the family of Prime-Flex polyurethane grout products, call our technical help line 800-321-7212.
