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Drain Pipe Sizing

How to Select Pipe and Elbow Heaters to protect your Drainage System

UltraHeat Pipe and Pipe Elbow Heaters are designed to protect the drain pipes from freezing in cold weather. Specifically the pipes and elbows attached between your waste-water holding tanks and the termination or low point gate valve.

This area of your system is the first portion of the drainage system that will collect fluid, and also be the first part of the system to freeze in cold weather due to the lower volume of fluids. Not only will frozen pipes prevent you from dumping your tanks it can also be the cause of broken ruptured pipes, knife valves, and holding tanks due to the expansion of the fluid as it freezes.


This scenario is not only a major inconvenience in the use of your RV; it can also be extremely expensive to repair. Once your RV has the appropriate amount of UltraHeat Tank, Pipe and Pipe Elbow Heaters installed, then your RV's drainage system will be fully protected for cold weather use.

There are many different types of RV's manufactured by multiple different RV manufacturers. Even within a single product line RV manufacturers produce various models of RVs.  Each design will have a different floor plan and all with a distinct drainage system and drain pipe layout.  It is not practical to have a "kit" or prepackaged sets of heaters for freeze protection.  Because of this, each drain pipe sizing and layout on every individual RV must be evaluated to determine the necessary amount and type of Heaters to be used.

Equally important is the spacing of the Pipe Heaters on the exposed drain pipes and elbows. Pipe and Elbow Heaters must not be spaced too far apart (no more than 2" (5 cm) spacing between pads) or freezing will occur between them. To get good protection, it is crucial to pay attention to your RV drain pipe heater selection. Select the correct combination of Pipe and Pipe Elbow Heaters and space them appropriately. Follow the steps below to determine the number of Heaters you will need for your unique drainage system.

Step No. 1: 

You must be able to visibly see and touch all the drain pipes and elbows that empty waste from your holding tanks in order to gather the drain pipe sizing and other information necessary to select the appropriate heaters.  In some cases, you might have to remove a belly cover or create an access hole and panel to gain access.

Step No. 2:

Note the number of 1½"- 2" and 3"(3.81-5.08-7.62 cm) diameter elbows in each of the drain pipe runs from the gray and black holding tanks down to the knife or dump valve(s). These elbows can be 90°, 45°, 22.5°, short sweep, long sweep, etc.  Each one of these elbows will require its own heat panel for protection against freezing. We have designed the AM-EH-158 Elbow Heater for 1½" or 2" (3.81-5.08) fittings and AM-EH-313 Elbow Heater for 3" (7.62 cm) fittings.

Step No. 3:

Measure the length of all individual straight drain pipe sections between both the gray and black holding tanks to the respective knife or gate valve. Again these pipes will be 1½"- 2" or 3"(3.81-5.08 or 7.62 cm) in diameter. The length of each measurement should include only the straight part of the drain pipe, and may include a short section of the coupling.

Make a list of all of the drain pipe sizing measurements for each individual section.  It may be helpful to sketch how the entire drain system is configured, from the tank drain portal to the knife valve. These RV drain pipe heater dimensions will help you select the correct pipe heaters. Each individual section of drain pipe will require a specific Pipe Heater(s) to be fully protected from freezing. Depending on their length, some pipes could require multiple heaters and they must be evenly spaced so that the heat applied will be uniformly distributed to provide proper freeze protection for the entire straight section of drain pipe.  If possible, we recommend no more than 2” (5 cm) between heat panels.

For 1½ pipes we offer a 12” heat panel, AM-PH1512 and an 18” panel, AM-PH1518.

For 3" pipes we offer a 18" heat panel, AM-PH312 and also an 18" panel, AM-PH318

Note:  Elbow Heaters can also be used to protect short sections of exposed straight drain pipes alone or in combination with Pipe Heaters. 

They can either be used like a Band-Aid around a finger, covering 3 – 5 inches (7.6 – 12.7cm) on 1.5” or 3” (3.8 or 7.6 cm) piping, or lengthwise along the bottom of the pipe. 

For 1.5” (3.8cm) pipe, the AM-EH-158 can cover 4” to 8” (10-20cm) of pipe, and the AM-EH-313 can cover 8” to 12” (20-30cm) of 3” (7.6cm) pipe along the bottom.    


Step No. 4: 

If you intend on protecting your freshwater holding tank, measure the ½” pipe tubing length between the holding tank and were it passes through the floor.  You will need one AM-PH-513 heat panels for each 12 inches of length.   For longer lengths, consider using our Smart Heat Cables sold in three sizes and can be modified in the field for length.   These smart cables can be used on any type of tubing from vinyl to Pex style.


Note:The PH-513 heat panel can only be installed on rigid plastic supply lines like "Pex", do not install on either vinyl or vinyl reinforced fresh water supply lines, they will melt.  Use our smart cable instead.


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