What should I do in this situation? What to do when the rain volume exceeds the drainage capacity of the rainwater chain?
We are often asked about rain chains because they have less drainage capacity than conventional downspouts, and they are not able to handle the rare, strong rainfalls that are expected.
I want to share with you some examples from the past of how we, together with our customers, have dealt with these problems.
1.Conditions of Installing Rainwater Chains
We would like to present to you the following scenarios:
・ Newly built factory (with offices)
・ Drainage by suspending a rainwater chain from PVC pipe
Around the perimeter of the factory, PVC pipes are connected from the horizontal gutter to the vertical downspout using roof drains, and a rain chain was used as a design feature at the end of these pipes. We visited the building just before it was completed and found it to be a very esthetically pleasing building that did not resemble a factory.
Below is an illustration of a rain chain installation, which does not directly connect the fittings to the PVC pipe, but opens a space to catch the water, so that even if the rainwater chain cannot drain the entire load of water, it can be diverted from the building to the ground regardless.
2.How Water Flows Through PVC pipes
Water flowing through a vertically installed drainpipe will normally fall down along its interior wall surface, so if left alone and the rainwater chain is installed as is, no water will flow down the rain chain.
In order to install a rain chain and properly channel water into the rainwater chain for drainage coming down from the PVC pipe, the water must first be collected in the center of the pipe and channeled to the rain chain.
3.Exclusive Fittings for Connecting PVC Pipe and Rainwater Chains
Seo Inc. has a metal fitting called a "PVC pipe connection fitting" that can be attached to the end of a PVC pipe to narrow the water flow and allow for the attachment of a rain chain. However, sometimes this would reduce the drainage capacity of the PVC pipe, resulting in insufficient drainage capacity.
In such cases, we customized the drain pipe connection fittings so that they are not directly connected to the PVC pipe, but are slightly separated as shown to create a water catchment, thereby ensuring the drainage capacity of the PVC pipe by overflowing at the very top of the rainwater chain when large amounts of water flow.
Currently, there are several other buildings besides this project that have been constructed in this manner, and so far, we have not heard of any particular problems.
4.Summary of the Presented Installation Method
However, there are several problems with this installation method.
・Will drainage of the overflow water be a problem?
During heavy rains, a significant amount of water will overflow and splash directly under and around the rainwater chain, so it is necessary to consider whether this will be a problem.
・Is it possible to install a drain connection fitting directly under the PVC pipe?
Since the fittings will be attached to the side of the building and the rain chain will be hung from that side, it will be difficult to install at a distance from the building due to loading problems. In addition, it is necessary to custom-make fittings to match the building and install them, which may increase the cost some degree.
The above is a way to supplement the drainage capacity of the rain chain that connects to the PVC pipe, but since the above-mentioned problems may arise, careful consideration should be given to whether this method will work in your situation.
