Every sewer has them… every few hundred feet… you can’t avoid it if you are in the sewer industry... Got a guess?... That’s it… MANHOLES. Ahh yes, the beautiful window to our lovely sewer underworld.
One of the most common questions asked by those first getting involved in the sanitary or storm sewer industry is, “How do you connect a profile walled plastic pipe (e.g. Contech’s A-2000 PVC Sewer Pipe) to a manhole?" The answer? There are three common methods used today:
- Flexible Boot Connection
- A-LOK Connection
- Grout-in-place Connection with Water-stop gasket
For the sake of this example, I will continue to use Contech’s A-2000 Profile Walled PVC Pipe as the example pipe product.
1. Flexible Boot Connection
The most common is the Flexible (rubber) Boot Connection. This is a connection to a rubber boot that is already attached or pre-casted into the manhole by others. The pre-caster who is contracted for the project uses various manufacturers to obtain these boots for various types of pipes. They always need to know what type of pipe is coming into the manhole whether it is RCP, HDPE, SDR, CMP or A-2000 etc. A-2000 is pushed into this boot and the contractor then uses stainless steel straps to seal the boot to the pipe. The question that arises is what do we do about the exterior corrugations. A “Manhole Gasket” is used to fill the corrugations and provides a flat surface for the stainless steel strap to hit. Using 2 per boot or 4 per manhole is preferred where there is an up-gradient and down-gradient connection.
2. A-LOK Connection
Some areas prefer to use an A-LOK Connection. Especially large diameter pipe sizes where the precaster does not have a large enough coring device for sizes like 36”. This connection is made when the pipe is pushed into an A-LOK hard rubber ring that, again, is precasted by others. A correct A-LOK Ring No.’s must be used for A-2000 diameters and outside dimensions. Once the correct ring is used by the precaster, a separate PVC sleeve is supplied that is made specifically for insertion into this ring. The sleeve acts like a bell to A-2000’s spigot and the typical double-fluted gasket is used while joining the two. Once the sleeve is on, then insertion into the manhole can be completed. Some contractors find it easier to insert the sleeve into the manhole first, and then stab home the pipe.
3. Grout-in-Place Connection
A-2000 can be grouted into the knock-out or mouse hole with a non-shrink grout. This is most common in Storm Drainage Applications. When this is done, we recommend that a “Water-Stop” gasket be used with this connection. Concrete/Cement/Grout does not adhere well to PVC. An elastomeric rubber gasket is required to provide a bonding surface. We use our typical double-fluted sanitary gasket for this connection. As you will see on page 6, for 8” and 10”, we recommend two gaskets. For 12” – 36” we recommend using one.