PPL Motorhomes: This New Year, Fix that leaky holding tank

OK, so you know that your holding tank is leaking, and since we’re being honest, it’s been leaking for a while. You can’t fool RV Nana. Think of the new year as your chance to fix that leaking holding tank. If you have a leaking holding tank, make it your new year’s resolution to fix it.

So, what is the next step?

Many people believe the only thing you can do is replace the tank. That option can be very expensive – from $300 to $800 or more.

Even worse, it also takes your rig out of commission for a while – maybe several weeks. Tank replacement is an inconvenience for someone who uses their rig occasionally, but for the full time RVer it is much more than that.

What about repairing the tank?

If you have a leaking tank, look for the cause. If it is inherent weaknesses in the tank causing cracking there is not much can be done to prevent it. But if the problem is due to external damage or stresses, look for a way to prevent re-occurrence of the problem. If the tank is being damaged by dragging, simply adding drag wheels on the rear of your rig may eliminate the problem.

One important point if you are taking your unit in for repair. Make sure the tanks are flushed out and clean. Leave the dump valve open and let the tank dry out. Many service centers will not work on the holding tanks if they have not been thoroughly cleaned. Of course, the exception to this is if you are unable to dump and flush the tanks due to a malfunctioning valve, etc.  If they do accept it to work on, you are going to get charged extra for the cleaning. Just remember, dumping and cleaning your own tanks is bad enough. If the service center has to take your rig to the dump station, dump it, clean it and maybe wait for it to dry, you are going to be paying for it.

There are basically three options of repair depending upon the type of tank you have.

Topical Adhesives – These are generally the two part epoxies that are normally used as a temporary repair. Since there is no adhesive that will permanently bond to LDPE or ABS, they are usually applied to plug a small hole or crack and are used with limited success. If the surface is roughened to allow better gripping and if they can be applied where there is little or no flexing, it increases the chance of success.

Since these adhesives are not of the same material as the tank, the difference in temperature expansion/contraction also plays a role in their successful use. Hot water run into a tank on a cold day can cause a major expansion/contraction that will loosen the grip of these adhesives. Most of the “Tank Repair Kits” that are found on the market are topical adhesives.

Thermal Welding – This is the process of applying heat to melt the plastic together. There are several methods of thermal welding. Each requires different special equipment and some skills in using the equipment, depending upon the extent of repair. For this reason, a limited number of RV service centers offer thermal welding. Some service centers who offer this service do not guarantee it to work but when performed properly it is quite effective. You may be able to find other businesses in your area which also specialize in plastic thermal welding.

There are several simple thermal welding kits on the market for around $200 that can be used quite successfully for small repairs after learning how. This may be a practical repair option for someone with the time and patience to work with it. Even though it is a fourth or half of replacement cost, the welding kit can be used repeatedly.

Thermal welding is the only permanent method of repairing LDPE tanks and can also be used for ABS tanks. One of the problems of thermal welding is it can be labor intensive for anything beyond minor repairs. This can make it quite expensive. This needs to be considered when weighing the option of repair vs. replacement.

Chemical Welding – This is the process of using a chemical that melts the plastic together. The most common example of this is plumbing cement. The plumbing cement melts the plastic of the pipe and fitting together creating a strong bond. Many times a plastic resin is added to the chemical to give extra sealing body to the joint.

Chemical welding works very well with ABS as a quick and permanent repair. Since most RV holding tanks are ABS, chemical welding is the most economical and efficient means of repair.

One of the advantages to chemical welding is the flexibility and ease of application. If you can reach the area with a paintbrush, you can repair it.  It can be used with any size crack or hole and over large areas to strengthen the tank.

Another is, the tank can be put back into use within hours. If you are a full timer or waiting to use your rig this can be a big advantage.

Make a note of this, the major cause of failure for any type of tank repair is lack of cleaning and not prepping the tank properly. Make sure to follow the manufacturer’s instructions for prep and application for the product you are using.

So, the next time you look under your rig and see your holding tank dripping, consider some of your options. Don’t just give up to replacing it when you may be able to repair it for a fraction of the cost.