If your motorhome routes rain through small roof holes and into hidden flexible pipes instead of open gutters, welcome to a common motorhome headache: clogged internal gutters.
Gutter systems
On many motorhomes, integrated roof gutter drains are incorporated into the RV’s roof. When water hits the roof, it flows into the factory-cut roof drains. Then the water runs through a hidden length of tubing built into the coach’s body and exits at the bottom of the rig.
The arrangement is nice because you won’t fight the dreaded black streaks that can come from other gutter configurations. However, if debris and dirt get into the internal pipe gutter, a clog may form and be difficult to dislodge.
Making matters worse, because the drains are internal, you can’t peek into a channel or scrape debris away. You need to know how to safely clear them.
Potential costly problem
When grit, granules, pine needles, seeds, or roof scum wash into those roof holes, they can pack down and slow or stop the flow. (This can happen even with a screen over the holes.)
Slow drainage can make water run where it shouldn’t. This might mean down sidewalls, into seams, or into trim pockets.
Over time, moisture can stress sealants, stain exteriors, and, in the worst case, find its way into the structure and cause soft spots or leaks that are expensive to fix.
How do you know?
So, how do you know that you have a clogged internal gutter pipe? If your air conditioner is running but you see no water dripping from the bottom of the coach, you probably have a clog. Why? The air conditioner will cause condensation, and that moisture is supposed to run off the roof through the roof holes.
Next steps
Once you’ve established that a gutter line is blocked, you can follow these steps:
• Park, stabilize, and inspect from the ground. Park level, chock wheels, and use a helper with the ladder. Walk the perimeter and look for streaking, pooling, or where water is dumping. Those clues tell you which of the drains to address first.
• Remove any small inlet piece if present and clear the shallow bowl. Many coaches have a little inlet cup or plastic grate at each roof hole. Carefully pry off that piece (keep the screws) and scoop the loose grit and leaf bits out of that bowl. Even a modest amount of packed silt there can trap water. If that part is fastened with sealant, be gentle so you don’t damage the surrounding trim. (You can always use Dicor afterwards to reattach the screen or grate.)
• Flush the line. From the roof, run a steady stream (not full pressure) into the inlet and watch the exit at ground level. If water backs up or bubbles, try the opposite approach. At the lower exit fitting, feed the garden hose up into the pipe or insert a 1/4″ PEX tube up into the drain and push/pulse water to dislodge debris.
Many RV owners report success by pushing a short length of PEX or a flexible rod from the bottom up to break packed material loose, then flushing again from the top.
• Use suction or simple tools. If water flushing doesn’t do the job, place a shop vac over the inlet or the exit and try to suck the clog free. Alternatively, run the flexible PEX gently through the line and guide the blockage out. Be cautious so you don’t tear a liner or pull a screw through the pipe. Community RV troubleshooting threads and pros suggest removing the duckbill located at the bottom of the drain. (It can hold back the clogged materials and prevent the water from flowing freely.) Then clean and reinstall it.
• Final test and reseal. When the line runs clear, test by pouring a steady flow of water into the roof inlet. It should exit freely and without overflowing along the roofline. Replace any inlet screens, fasteners, or rubber valves you removed. Reseal disturbed areas with RV-grade sealant where necessary.
• Prevention tips. Keep the roof and inlets free of loose debris by brushing or rinsing the roof after heavy leaf fall or storms. Consider light mesh guards or strainers that sit over the inlet bowls to keep large particles out while still allowing flow. Small upgrades like a gutter strainer can reduce how often you need to clean.
You can watch a video of a similar process here.
DIY fixes
Many DIYers posted their own fixes on various group threads and posts. Here’s a sample:
One DIYer used one of these to keep debris out of his drain line. He says, “They work great to strain out leaves, seeds, and other debris. You do need to check and replace them because the sun will degrade them over time.”
Another DIYer uses this chainmail to help keep dirt from entering the drain line. “I’ve used this for three years now with no problems at all.”
Both motorhome owners say they simply rinse any dirt that gets inside their “strainers” and put them back in place.
“I just use my air compressor to blow out the line,” another DIYer offered. However, Newmar cautioned one owner not to use more than 30 psi when attempting to blow out a clog in the drain line. Too much air (or water) pressure can damage connections and/or seals.
Call in a professional
If the roof membrane looks soft or you find structural damage, take the coach to a qualified RV service center.
If clogging reoccurs after you’ve cleaned lines and resealed, there may be routing issues, collapsed tubing, or factory fittings that need replacement. Those are jobs for an RV shop.
Have you ever experienced a clogged internal gutter on your motorhome? How did you fix your problem? Tell us in the comments below, please.
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RVDT2770
Sounds like a feature to avoid when shopping for an RV.
Part of the issue, at least with Newmar’s design, is the piping that runs from the cup to the ground at each corner is only 1/2″ ID! That small diameter clogs too easily. I know they cannot go too large, but even 3/4″ ID would help.
Many of us on the IRV2 Newmar forum have removed and left the duckbills off completely. No one has reported issues with wasps making mudnests due to no duckbills to supposedly stop them from entering the tubes from below.
Frankly, I’d rather not have the system at all.
Sounds like a really stupid design. I have been rving for 25 years and have never heard of this. I wonder if this is only Newmar, or are there other manufacturers doing the same thing? Sure glad I didn’t have that on my Winnebago dp, or on my current Class C.
It’s not just Newmar. Many higher end brands have these. I’ve even heard of some brands that have specific AC drains of similar design embedded in the roof! 😵💫
The duckbills are one of the major issues because they impede the flow in the tube. In addition, they are usually held on with a screw that extends into the pipe creating a point for junk to catch on. Removing those removes the biggest headache with the system, but the design could still be better.