How To Calculate Gutter Downspouts?

One of the aspects that must be considered when installing rain gutters is the number of downspouts that we have to place. As well as the diameter of the ducts to ensure that it correctly fulfills its function. Although this issue should be solved by All About Gutters Inc professional storm drain installation company that is going to do the work, we tell you how to calculate downspouts so you can get an idea.

Why do you have to calculate the number of downspouts?

First of all, it is important to be clear that the downspouts are essential and that the number to be placed should not be calculated lightly. We can still find people who determine the ducts to be installed by simply measuring the length of the facade and estimating the placement of a downspout every few meters. However, this calculation is wrong, since there are other factors that we must take into account.

The downspouts are responsible for evacuating the water that is collected in the upper ducts from the roof. So in case of not putting the sufficient number we will find rain systems that are not capable of managing the water at a time of precipitation. Causing the channels to overflow , with the risk of leaks that this supposes for the construction, that the water accumulates with the danger of breakage due to excessive weight or that jams appear .

Factors to take into account when calculating the number of vertical ducts

In order to determine what we should look at when counting downpipes, we must consult what the regulations contained in the Technical Building Code and Health Document No. 5, CTE-HS-5 say. Thus, the aspects to consider are:

Roof surface in horizontal projection. That is, the square meters that you have.

Rainfall intensity of the area. To be consulted in the tables provided in the HS-5.

Slope of the gutter where the downspouts are to be placed.

Once we have these data, we only have to make the corresponding calculation and follow the indications set out in the tables provided in the CTE.

Formula for calculating downspouts

Below you can find the calculations that must be done to determine each data and be able to know the diameter corresponding to the downspouts to be installed.

Calculate the area corresponding to each downspout.

Correct the surface . For this, it is necessary to know the rainfall in the area that we can find in one of the annexes of the HS-5 and apply it to obtain the correction factor.

Once we have the corrected data, we only have to consult the corresponding table in which the nominal diameter for the downspout in question is indicated.

As can be seen, although at first it does not seem a particularly difficult question, it is necessary to have some experience to be able to make these calculations fluently. As well as having sufficient knowledge of the CTE. For this reason, it always has professional installers who guarantee a correct installation of the rainwater system.