No house can function today without water. The most important thing here is the correct cable diameter for the respective task of the cable. These diameters are common today:
Fresh water
First of all, it is important that the fresh water gets to the places where you need it. There are fresh water pipes for this which either only transport cold water or are supplemented by a second pipe for warm water. Regardless of the temperature, the cable cross-sections should be selected in such a way that some basic effects are achieved:
- Provide the need for fresh water
- Reduce the length of time the water remains in the pipe to prevent the development of germs as much as possible
- Maintain a flushing effect in the pipe to avoid deposits and clogging of the cross-section
As a result of these requirements, in contrast to common attitudes, it is not a question of always installing the largest possible fresh water pipe. Instead, the cross-section should be chosen so that, on the one hand, the necessary water is available at the point of consumption. On the other hand, the dimension should be like this
be low so that the water flow avoids deposits and at the same time a long service life in the pipe is not to be expected.NOTE: Especially when the water is warm, there is a risk that so-called legionella, a dangerous pathogen, will multiply in the water. In addition to a high temperature, a frequent exchange of the water protects against the infestation. This exchange takes place via a regular withdrawal of the water from the pipe.
The cross sections
Unfortunately, it is not possible to determine which pipe cross-section is ideal for fresh water. The higher the requirement, the larger the cable cross-section should be. The longer the line to the consumer, the thinner it should be in order to avoid water standing in the line for a long time. Therefore, in most cases, the cable cross-sections are calculated. DIN1988-300 and DIN EN 806-3 specify the maximum cable lengths that may be installed depending on the water volume and the pipe cross-section.
As a rough guide, however, you can use these cross-sections as rough guide values for the fresh water pipes:
- Main connection domestic water: DN32, in the new building now and then also DN25
- Main line to the storeys: DN20 or DN16
- Subsidiary lines to the end user (Shower, sink, etc.) DN16 or DN13
- Subordinate branch lines (e.g. B. Garden pipe) DN13 or DN10
NOTE: "DN" means "diameter nominal" and indicates the usable inner diameter of the pipes in millimeters.
sewage
In contrast to fresh water, the wastewater also carries countless other things in addition to water:
- soap
- Oils, fats
- dirt
- Leftovers
- Feces
Therefore, in addition to the actual water transport, it is particularly important for the sewage pipes to to safely discharge the substances carried and at the same time to prevent the cable cross-section from clogging. The so-called flooding effect of the water within the pipe is therefore important. This means that the waste water carries away solids so that they do not remain in the pipe. With the usual gravity pipelines, it is ideal not to have as large a filling as possible within the pipeline. Instead, only around a third of the cross-section should be covered by water. Then the entrainment effect is greatest and the line remains permanently free and continuous. Therefore, the usual cross-sections are also based on the type and quantity of connected consumers. A calculation is also required here. The valid one
The basis for this is DIN1986. The following diameters generally result in a single-family house:Connecting cables
- Wash basin: DN30
- Sink, dishwasher, washing machine, shower, bathtub: DN50
- Collecting lines of the above-mentioned objects: DN70
- WCs: DN100
Downpipes in the building
- Sewage: DN100
Ground lines under the building:
- At least DN125
Rainwater
When draining rainwater from terraces or roof surfaces, the necessary pipe cross-section depends primarily on the surface connected to it. Downpipes with DN70 or DN100, which merge into underground pipes in the ground with DN100 or DN125, are typical.
ATTENTION: Some municipalities generally stipulate certain pipe diameters for the drainage pipes in their area of responsibility. Usually these are minimum cross-sections with DN125 or even DN150. The main aim is to keep lines that may have grown over time still sufficiently large.
Other cable cross-sections
In addition to water and sewage, there is of course a number of other supply media in every house that are made available in pipes. This is primarily about gas and electricity, and possibly oil from your own tank for heating. However, these media have an increased risk, so that only specialists are allowed to work here. These also carry out the dimensioning based on current regulations.
