Slide Out Leaking at Bottom Corner

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Slide-outs are terrific to use once you’ve parked at the campsite and wish to settle in. The added internal space makes them a no-brainer, but with older RVs, they can be troublesome.

RV buyers might ask, “Do slide outs leak?” You bet they do.

No one brand isn’t susceptible to the problem. For instance, Keystone RV slide out leaks do happen, so don’t be fooled into thinking with a better RV manufacturer’s brand, it’ll never happen to you…

Unexpected slide-out leaks can create surprises for RVers wanting a relaxed evening with their feet up watching Netflix.

When your slide out is leaking at the bottom corner, or elsewhere, then it should be quickly attended to.

It may start as just some dripping water or discovering damp carpeting, but any water ingress should be taken seriously. This avoids the situation from becoming worse over time through inattention.

Slide Out Leaking at Bottom Corner

A slide out leaking in the bottom corner is a bad sign. Likely the RV slide out bottom seal has deteriorated and is no longer working well.

Any investigation into the source of the leakage may also cause you to uncover another slide out leak problem area too.

RV Slide Leaking: What Causes a Slide Out Leak?

A slide out can leak for several reasons. It can happen only when the slide out is open, when it is closed, or at both times.

Slide-out leaks appear usually because of the following reasons:

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  • Older RV slide-out showing its age.
  • Worn seal causing an RV slide out seal leak.
  • Bad fitting with the parts, i.e., the flange warping allowing water inside.
  • RV slide exterior deterioration allows water ingress.
  • An inferior part is not up to standard.
  • Blocked weep holes. These holes relate to locking and unlocking the slide-out and often get overlooked.
  • RV Roof or gutter leaks can cause excess water to reach the slide-out and find its way inside.

Find the Slide Out Leaks

Look both for leak spots and the possible cause of them.

Don’t only assume that the bottom corner of the slide out is leaking and nowhere else. That would be a mistake.

Instead, look around the entire slide-out to confirm that that’s the only place. Not only is this good practice, but there may be different causes for each leak spot.

The tell-tale signs of leaks beyond the water itself are rust areas, warped materials, or general discoloration from normal.

It’s useful to clean up the area, wait until it rains and check where the water is coming in from? Water can gain entry inside the RV and then travel along a path before it reaches the slide-out corner.

Also, it doesn’t necessarily need to have a crack or damage to a flange or seal, although they’re the most likely causes.


The floor will feel spongey if it’s absorbed moisture. If there are any cabinets in the slide-out interior, check inside those too.

Inspect the Seals

The seals are particularly vulnerable to age, damage from the sun, and debris getting inside them.

The more a slide-out is utilized, the greater the chances of wear and tear on the rubber seals and the silicon material. It’s the most common RV slide out leak repair problem.

When cracks become visible in the seals, then they will likely need replacing. Seal cracks let water inside and those cracks will only widen with time.

It’s a good idea to add some RV seal conditioner product over the seals every couple of months. This can protect them from drying out, becoming inflexible, and then cracking.

When living in a humid climate, that’s even truer and possibly should be done even more frequently.

Thetford Premium RV Slide Out Rubber Seal Conditioner & Protectant – 14 oz (Model 32778)

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How to Fix a Leak in a Slide Out

Whether you’re fixing up the fifth wheel slide out or waterproofing camper slide out for the first time, don’t fret. Sealing RV slide outs is not too difficult:

Replace Old Seals

Replacing old seals before they become fragile is better than being caught out.

A flood inside the RV is going to be far more expensive to rectify and avoid permanent moisture damage compared to a little due diligence in swapping out old seals.

The seals (and the flange too) don’t last indefinitely. If purchasing the RV previously owned, assume that seal maintenance hasn’t been done. Likely, the seals will need replacing very soon.

Pay attention to the type of seal because there are different types and sizes. They need to be both the right width and length to fit correctly. Sold per foot, they are usually between $2-4 for each foot of seal required.

When removing the old seal, be sure to dry out any internal area that contains water. Once dry, apply a new seal.

Do test the new seal by moving the slide out into position and then closing it again. The seal needs to be fitted perfectly, so it doesn’t get out of position with the movement of the slide-out. This test avoids losing the seal after replacing it.

Seal Screws Are the Culprit?

Sometimes, the screws that secure the seal are responsible. In which case, they’ve probably rusted away.

Also, be sure that the slide-out doesn’t have collected dirt near the screw location that could be damaging them.

Remove the screws and replace them. It is the only solution here. Also, add some protective coating that’s weatherproof to prevent water from causing damage at each screw’s location.  

Use Sealant to Protect Seals and their Screws

Seals and screws are only as good as their conditioner and sealant.

As mentioned earlier, an RV seal conditioner should be used every 60 days to avoid the seal from cracking. It’s also sensible to use lap sealant for the screws to ensure they remain impervious to water penetration.

For example, the Thetford Conditioner and Protectant for RV Slide Outs protect the seals from drying and cracking. It just sprays on, so it doesn’t create any mess or fuss. Easy maintenance!:

Thetford Premium RV Slide Out Rubber Seal Conditioner & Protectant – 14 oz (Model 32778)

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If you click this link and make a purchase, we earn a commission at no additional cost to you.

Slide Out Leaks When Closed

A slide out can leak after it has been closed. This might be surprising but it’s not as uncommon as you’d think.

Having been open, the slide out can accumulate debris beneath it or above it that reaches the interior or the seals.

If the slide out is then retracted, the debris could get into the mechanism and cause damage to the seals by rubbing on the rubber compound weakening or destroying it.

This issue will make the seals prone to cracking and subsequently allow new leaks.

The seals might have been incorrectly fitted or refitted when replacing them, weren’t ideally positioned, or were the incorrect size. Any of these could cause a seal to pop out when the slide is closed and create an access point for future water ingress.

Slide Out Leaks When Open

A slide out is likelier to leak when open than when it is closed.

Water can reach the roof of the slide-out. Also, if the arm supports are permitting the slide-out to rest at an uncomfortable angle, then water can pool up.

Any cracked seals or debris accumulated could allow water ingress during heavy rainfall too.

Should You Get an RV Slide Out Rain Guard?

An RV slide out rain guard can protect from water hitting the slide out and reaching the edges where it might find cracks to exploit.

Similar to a rain guard on a car door frame, they prevent rainwater from reaching the sides of the slide out by deflecting it.

It’s possible to use either a slide out rain guard or to attach a plastic shield along the most vulnerable edge of the slide-out. However, when using the latter as a DIY solution, it needs to stay in place during travel too. So, bear this in mind.

Either rain guards, rain deflectors, or even a slide out topper will reduce the amount of water reaching the slide out.

Closing Thoughts

Don’t delay if your slide out is leaking at the bottom corner or elsewhere. The causes are usually relatively simple to isolate and are often a result of poor RV maintenance.

Fix it before the moisture damage becomes a much larger problem for you.

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