LAYOUT FOR LENGTH OF RUN
The layout of a trench drain can be quite simple to extremely complex depending on the applicaiton. Most trench drains simply slope from one end to the other, however, some longer trench layouts can require multiple outlets, the insertion of neutral (non-sloping) sections, or wall extensions. Be sure that you know the total length of the system to ensure that the system can slope the entire length of your run. If the system is not capable of sloping the entire length of the run then you will need to specify how to get the desired run length. Will you allow neutral channels, should multiple outlets be taken, or should wall extensions be used?
ONE DIRECTION (TYPICAL LAYOUT)
Standard run length for most systems is about 100 linear feet. For run lengths less than the standard length simply choose the depth channels you desire. It is customary that if nothing is specified you will get the shallowest drain possible for the desired run length to reduce installation and material costs.
STEPPING LAYOUT TO EXTEND RUN
If the run length exceeds the standard run length you can add neutral channels in the run to extend the run length. By doing this you lose some hydraulic capacity and too many neutrals in a row can cause the flow velocity to be significantly reduced. This will allow debris to build up easier in the trench if flows drop below 3ft/second. This is often the most economical method to extend the run length where the system capacity is not in question.
SLOPE TO MIDDLE TO GET LONGER RUN LENGTH
By sloping to the middle you can use the standard system length twice often giving you 200 linear feet without the added cost of wall extensions and without having to use neutral channels. This technique is also useful when the invert depth is an issue. By running the slope both directions the system is only half the depth it would be if you ran the slope in only one direction.
MULTIPLE BOTTOM OUTLETS TO EXTEND RUN
With multiple outlets you can have an infinite run length without getting out of the standard run length. Again, you can keep the trench drain shallow using this practice.
WALL EXTENSIONS TO EXTEND RUN LENGTH
Wall extensions allow you to take the standard run length and start it over with a wall added to the top giving you an additional run length. In many systems there are two different wall heights giving you three standard run lengths. The wall extensions do increase material and installation costs and should therefore be avoided unless they are necessary. Most often these are warranted when a high volume of flow is needed and outlets are not possible along the run.
LAYOUT FOR TURNS & INTERSECTING TRENCHES
Many interior applications also require trenches to turn or intersect other trench drains. This is especially true in manufacturing and industrial applications where the trench drain need to surround a piece of equipment or turn around a machine to avoid conflicting with it. When designing turns try to keep them away from the ends of channel sections as they are more difficult to fabricate and the remaining grate sections may be very small. When small grates are left in the trench the lock down devices can be compromised causing traffic over these to cause the grates to come out. This can create a hazardous condition and should be avoided.
When making an intersection in a trench run or when intersecting an existing trench drain using prefabricated trench drain sections try to make sure that the trench is shallow enough that it intersects above the radius section of the trench you are tying into. If the trench is made to match the inverts on a prefabricated trench drain it makes the cut more complicated and you often get a gap below the trench that can introduce chemicals and bacteria behind the drain channels causing problems down the road. This is less an issue if you are using a forming system, but, it is still a good practice to follow.
For additional assistance with a layout or design please contact us and we will be happy to assist you.