Overview: drain camera
A drain camera, endoscope camera or sewer inspection camera is used to inspect pipes and lines without having to dismantle pipes or even break open the wall. The camera image can be used to detect damage to the pipeline or to determine the cause of a drain blockage.
To find out the cause of a drain blockage, a sewer camera is extremely helpful. The image transmitted from the camera head to the monitor via the sliding cable shows the reason for the drain clogging: deposits or blocking objects become visible. Then the drain cable tool ideally suited for removing the drain blockage can be used. In addition, it can also be determined whether drain cleaning is possible at all, or whether the pipe is damaged and needs to be replaced. Following a drain cleaning, it can also be checked whether the blockage of the pipe has been completely removed or if further work is necessary.
For a professional drain inspection it is immensely helpful if the pipe camera has a recording function. In this way it can be precisely documented which damages or blockages are present in the pipe. These can be photographed, or the entire drain inspection can be recorded on video. A before and after comparison is also possible.
Structure of a drain camera
The drain camera or drain inspection camera has a waterproof camera head. This contains the actual camera module, which is required for image acquisition. In addition, the camera heads are equipped with powerful LEDs for illumination, as there is not enough light in the tube to be examined. Sufficient illumination in the tube is essential for the quality of the transmitted image! Even a very good camera sensor with high resolution cannot transmit a reasonable image without appropriate illumination of the pipe.
The camera head is the most important and at the same time most sensitive part of the drain camera. For tests in sewage pipes, it must necessarily be watertight. However, it is exposed to enormous stresses in the pipe due to deposits, calcification and branching. At the same time, the waste water is often aggressive or contains fats and oils that adhere to the camera head. As a rule, the heads are therefore made of stainless steel and have sophisticated sealing mechanisms to protect the sensitive electronics from moisture and contamination. At the front, in front of the CMOS camera sensor, there is a pane of extremely hard and scratch-resistant glass. This sapphire glass is basically the same as the glass known from the mobile phone display. Usually this sapphire crystal is additionally coated to achieve a lotus effect, i.e. a simple pearling off of water, grease, oil and other liquids.
The diameter of the camera heads varies depending on the pipe diameter. For pipes with a diameter of 50mm that are commonly used in households, the diameter of the cameras is usually between 23mm and 30mm. On the one hand, these are curve-capable enough, but on the other hand they offer enough space for a high-quality camera module to be able to provide an adequate resolution of the image: The higher the resolution, the better details in the tube and the condition of the tube can be seen. The camera head therefore always represents a compromise between size and resolution. Modern camera heads with 30mm diameter are often already able to transmit a picture in "HD", i.e. with 720p or even 1080p. Small camera heads with a diameter of 12mm to 14mm are perfect in narrow tubes from 30mm or more or in heavily clogged tubes, however, as they are extremely small and bendable, they provide a worse image. For pipes of 100mm and more, camera heads with a diameter of 40mm or more are often used, which provide Full-HD images and videos. There is sufficient space in the pipes in which they are used, but a high resolution is very helpful to be able to see and inspect the large pipe diameter in detail.
High quality camera heads also have a floating camera module. This has the great advantage that the camera image is always transmitted upright, "perpendicular", to the screen. If the camera head is also rotated several times along its longitudinal axis, the observer does not need to turn his head. Instead, gravity uses a small weight on the camera sensor in the camera head to ensure that the twisting of the head is not transferred to the image. The advantage is bought by the fact that the special mechanics for the floating camera module is prone to damage of the camera head.
Camera heads should only be used in conjunction with the guide balls provided. These are usually made of plastic and enclose the camera head in a ring shape. This not only has the advantage of avoiding direct contact between camera and pipe. At the same time, the guide ball centers the camera head in the pipe to obtain a better image. There are different diameters of the guide balls for this purpose. For larger pipes from DN100 upwards, special guide carriages are available, some of which have wheels on the edge to make it even easier to slide through the pipe.
Camera head with locating
Some camera heads also have a built-in location transmitter. This transmits a radio signal with 512 Hz or 33 kHz frequency inside the drain. With a suitable locating device the radio signal can be received and the transmitter can be located quite accurately. In this way, walls or soil can be broken up quite precisely at the desired point in the sewer system. Camera heads with locating are usually longer and possibly also stronger in diameter than those without locating, and therefore less flexible.
The more the radio signal reaches the receiver, the more accurate the locating process is: thick walls, metal pipes, iron in the wall or several metres of soil between transmitter and receiver make exact locating difficult.
Pushcable with reel
The camera head is connected to a push cable. The push cable, also known as push rod, is a particularly stable, yet flexible fiber optic cable. It is used to push the camera head into the drain and guide it inside. Like the camera head, it is also subject to extraordinary stress and must therefore be extremely robust. Fibre optic cables are often used. Especially the outer insulation jacket of the pushrod cable suffers greatly from the conditions in sewage pipes. Not only do the substances contained in the wastewater attack the material. The mechanical effect of the deposits, edges and encrustations in the drain can peel off and damage the pushrod. In addition, many of the push cables must not be bent too much and too often in a row. 180 degree bends, for example, will cause the cable to break and be destroyed. A maximum curvature of the cable of 87 degrees at most must therefore almost always be observed.
The push cable is often only 30-50cm long for small hand-held tube cameras. These are designed for use in the siphon up to the first bend behind it, and are simply screwed directly onto the hand-held unit. For larger drain cameras used for pipe inspections in households, the length of the push cable is usually 20m or 30m. Even if e.g. 30m cables are rarely unwound completely, this has advantages: push cables often bend in the front area behind the camera head, because this section is most stressed when pushing and guiding. Depending on the design of the cable, it may be possible to cut it off behind the kink and reuse it after soldering the connector. For pipe inspection in large diameters, drain cameras also have push cables with 60m up to 100m length. Similar to the camera head, the diameter of the cables used varies depending on the area of application of the cameras. For small pipe cameras, which are held in the hand, the diameter is often only 3-4mm, for the pipe cameras used in households, 5-7mm thick cables are usually used. For sewer cameras used to inspect public sewers, there are even stronger push cables with 9mm and higher diameters.
Longer pushcables are wound on a reel from which they can be pulled out and pushed back with a rotating bearing. The reel is either mobile and can be held in the hand. This system is mainly used for simpler camera models. The disadvantage, however, is that one or both hands are always required, which is disadvantageous when operating the camera system in parallel. Other reels are therefore permanently attached to the camera and can be operated more conveniently, as they often also have a function for clamping / holding the cable.
Modern cameras have an integrated meter counter. This uses a slip ring to measure how many meters of the push cable are pulled down from the reel. This has great advantages for pipe inspection, as it makes it possible to determine the depth at which the pipe is blocked or damaged. Then it can be determined how many meters of drain cleaning cable or flushing hose must be used, or whether the subsequent pipe cleaning is carried out at the correct position in the pipe.
Operating element or control of the pipe camera
The mobile or fixed reel with the push cable and the camera head is connected to the monitor and the control element of the pipe camera. The screen transmits the live image from the camera. The actual drain inspection takes place here. The push cable with the camera head is pushed through the pipe while the image transmission is analyzed on the monitor. If the pipe inspection camera has a meter counter, the number of meters is faded into the image.
Modern pipe cameras have a digital recording function. The Digital Video Recorder is often abbreviated as "DVR". In most cases, both photos of the screen content can be created, as well as videos that record the entire pipe inspection. Such documentation is very useful because it records drain blockages or damage to the pipe and the record can be used as evidence for insurance, successful pipe cleaning and other documentation purposes. The recordings are saved on SD memory cards or USB sticks.
Professional pipe inspection cameras usually have an integrated keyboard. This is either permanently installed or, in the case of very modern cameras, connected to the camera via a Bluetooth or other wireless connection. The keyboard allows text to be written in the live image of the camera. In combination with the recording, this is a very helpful feature, as it can be used to describe, for example, the damage. If a photo is now taken, not only the image of the camera is included, but at the same time a written documentation of the damage is also included on the photo. If the pipe camera records a video of the drain inspection, the inscribed text is also recorded and captured in it.
The pipe inspection camera usually has additional operating elements, which can be used, for example, to control the brightness of the LED of the camera head. If the camera head has a turn-off rod or a pan-rotor function, these are operated via a joystick or a similar control unit of the operating element.
Care and maintenance
In order to ensure that the pipe camera can withstand the heavy demands for as long as possible, it should always be maintained. It has proven to be very helpful if the sliding cable is pulled directly through a clean, damp cloth when it is pulled back out of the tube. This prevents coarse dirt and residues from the pipe from getting into the reel. The camera head should be rinsed with clear water after each pipe inspection in the sewage system and any residue in the spring behind the camera head should be removed. If the camera has been controlled using dirty fingers on the control panel, always clean it with a clean cloth. It is important to make sure that after use, any moisture is kept away from the pipe camera in order to avoid further unnecessary stress on the sensitive electronics: A waterproof camera head does not mean that the entire camera can be stored in a damp-wet environment, for example in a vehicle. Dry all parts or make sure that the pipe camera can dry completely. In this way you achieve the maximum durability of your equipment.