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What To Do If Your Tumbler Barrel is Leaking

Leaking tumbler barrel
Muddy water on the base of your tumbler indicates a leaking barrel. Leaking is usually caused by a build-up of gas pressure in the barrel.


What Are You Tumbling?

The most common cause of a leaking tumbler barrel has nothing to do with the barrel and everything to do with the materials in the barrel.

A few materials generate gas when they are tumbled. A build-up of gas pressure in the barrel will cause the water in your barrel to seep out around the edges of the lid. Here is a list of some materials that can generate gas and cause leaks:
  1. man-made glass
  2. natural glass (especially obsidian)
  3. man-made slag
  4. pieces of metal
  5. pieces of metallic ore
When these materials are tumbled, gas pressure slowly builds up in the barrel. The first sign of a gas build-up is usually a slight inflation of the tumbler barrel. This can be detected by looking at the bottom of the barrel to see if it is bulging.

If you don't catch the problem at that stage, pressure in the barrel can cause a few drops of water to seep out of the barrel between the lid and the edge of the barrel. Usually the operator of the tumbler will notice a small amount of muddy water on the metal base of the tumbler and stop the machine.

This is why, when someone contacts us about a leaking barrel, our first question is always... "What are you tumbling?"... "Is there even a few pieces of man-made or natural glass in the tumbler?"... If their answer is "Yes" we refer them to this article: Gas in the Rock Tumbler Barrel.

Now they know why their barrel is leaking. There is usually nothing wrong with their barrel.

A practice that we do ourselves and recommend to everyone is to visit your tumbler about once a day to so how it is running. If you see drops of muddy water on the base of the machine or if the bottom of the barrel is bulging outwards, then there is likely pressure building up in the barrel.

If pressure is allowed to build up, it could reach a level that is high enough to push the lid out of the barrel.

What Else Is In The Barrel?

People often add other things to their tumbler barrel - such as borax, soap, liquid detergent, clay and more. Some of these materials can also be responsible for a build-up of gas in the tumbler barrel.

We strongly recommend against using these materials. (The only exception is that we use a small amount of soap for a short period of time when burnishing.) Rocks can be tumbled successfully without any of them.

If you really want to try adding these materials to your tumbling, please visit your tumbler once or twice per day the first few times you use them. When you visit, be on the look-out barrels with bulging bottoms or seeps of water around the lid of the barrel. Once you use a material a few times with no problems, then it is probably safe to use with a little less caution.

Now let's consider your barrel... how it is cleaned, how it is maintained and its physical condition.

Seven Reasons Why Your Barrel Might Be Leaking

Most rock tumbler leaks are easy to fix. The leak almost always occurs where the lid and the barrel are in contact with one another. The most common causes of a leak there are listed below in their approximate order of frequency.
  1. Debris on sealing surfaces of the barrel or lid
  2. Lid is not properly seated
  3. Lid with rough edges or cracks
  4. Lid is not tightly secured
  5. Damaged lid gasket
  6. Lid is worn out
  7. Damaged barrel
Find seven fixes for these problems below...

Seven Fixes for Rock Tumbler Leaks

Clean the lid seat
The most important place to clean a rotary tumbler barrel is the rim where the lid seats. We use a toothbrush to scrub the rim of the barrel and the outside edge of the lid. Spend 30 seconds on this and you will rarely have a leak.

1) Debris on the Sealing Surfaces of the Barrel or Lid:

Small particles of grit or debris often cling to the rim of the lid or on the recessed part of the barrel where the lid seats. Water can escape in the tiny space produced by these particles. This is the most common cause of a rock tumbler leaking - just one drop of water at a time. Here's how to fix it.

Simply open the barrel and pour the contents into a container. Then, thoroughly rinse and scrub the barrel until every speck of grit and rock has been removed. Now, get a used toothbrush and thoroughly scrub the edges of the barrel lid and the part of the barrel where the lid seats (the accompanying photo shows where this scrubbing needs to be done). Make sure to thoroughly scrub the entire edge of the lid and the entire recessed part of the barrel where the lid seats. Just one speck of grit on either of those sealing surfaces can cause a leak.

Then, carefully pour the grit and rock back into the tumbler barrel, being very careful not to spill anything on the newly-cleaned rim. Tiny pieces of grit that are too small to see can cause a leak. Then, replace the lid and place the barrel back onto the tumbler.

Thirty Seconds of Prevention: To prevent this problem in the future, we spend 30 seconds thoroughly scrubbing the rim of the barrel and the edge of the lid every time we change our tumbler. Since we started doing this, we have had very few leaks.

Lid not seated properly
This image shows a lid that is not completely seated in the barrel. Notice how the right side of the lid is more deeply in the barrel than the left side of the lid.

2) Lid Is Not Properly Seated:

Sometimes the problem is this simple. When the lid was positioned, or secured by a retainer ring or threaded nut, it was either not straight or it was not firmly against the sealing surface of the barrel.

This fix requires emptying the barrel as described above, cleaning the sealing surfaces, returning the rocks and grit back to the barrel, and replacing the lid - and making sure it is straight before placing it on the tumbler.
Damaged lid
This image shows a lid with what appears to be minor damage - but a closer look shows that it could easily cause a leak.

3) Lid With Rough Edges or Cracks:

Some rock tumblers have a plastic or fiberboard lid. A rough edge on the lid can be a manufacturing artifact, or it can be caused if a lid is accidentally dropped or scraped against a hard object.

This problem can usually be solved by very lightly sanding the lid edges with extra-fine sandpaper. Don't sand so much that you round the edges of the lid. Just give it a very light rub on the upper and lower edges of the rim. Lid roughness can often be detected by rubbing a finger or a piece of fine cloth along the edges of the lid - the cloth will snag on the rough spot, a finger might feel it.

Wash the lid and the barrel before you put the tumbler barrel back together. If a light sanding does not solve the problem, try it again. If that doesn't work, or if the lid is cracked or badly damaged, a new lid is probably needed.
loose lid
It is easy to tell when the outer lid on a Lortone barrel is not tightened down all the way.

4) Lid Is Not Tightly Secured:

Many tumbler lids are secured by rubber retainer rings, wing nuts, or threaded nuts. Sometimes these are not tight enough to prevent leaks. Rubber retainer rings can stretch and become ineffective. Nuts not tight enough can make an incomplete seal. Care must also be taken not to overtighten, which can lead to a deformed lid and/or deformed barrel, which is another cause of leaks. Sometimes a new retainer ring is needed when the original ring has lost its ability to hold the lid securely.

5) Damaged Lid Gasket:

Many tumblers have a rubber lid gasket that serves as the sealing surface between the lid and the barrel. They can have cracks along their edges that can leak. Or, a small hole in the center of the gasket can allow water to escape from the barrel and cause a leak. These gaskets are inexpensive and easy to replace.

How to reinforce a tumbler barrel lid
We reinforced the inside of a tumbler barrel lid by GOOP-ing a thin circle of sheet rubber to the back of the lid. We use a reinforced lid when tumbling large pieces of angular rough that might cause excessive wear on the plastic lid. This is one of the tips that we learned in Steve Hart's book, titled Modern Rock Tumbling.

6) The Lid Has Worn Out:

The lids on rotary tumblers will wear out over time.

This is normal.

As the tumbler runs, grit and rough scrape against the inside of the lid. Over time, this will wear the center of the lid thinner and thinner. If not checked and replaced, this lid will eventually develop a hole, and a small leak, and it can cause a mess if not caught in time.

What do we do about this?

Inspection: We frequently inspect the lids of our barrels by pressing on them in the very center. You will be able to tell if a lid is wearing thin. It will be flexible in the center. We usually have an extra lid on hand to replace a lid that has worn thin.

Types of Very Abrasive Rough: If you are tumbling small (under one inch) pieces of rough, very little wear will occur on your lid. The most abrasive materials are large pieces of rough that are angular in shape and very hard. These include quartz and chalcedony (agate and jasper).

Steve Hart, the author of Modern Rock Tumbling, explains how to significantly prolong the life of tumbler lids in his book. We followed his suggestion and show the results in the accompanying photos. Here is what we did...


We cut a piece of 1/8" gasket rubber into a circular shape, about 1 inch in diameter smaller than the size of our lid. You can find sheets of gasket rubber here. If you have a small tumbler, you can protect a lot of lids with a 12" x 12" sheet.


We got a tube of Amazing GOOP and squeezed a thin circle of GOOP around our rubber circle. You can find Amazing GOOP here.


We placed the circle of rubber onto our tumbler lid and gently pressed around its edges until the GOOP squeezed out around its circumference - and allowed it to dry overnight.

7) Damaged Barrel:

This is a common problem in barrels that are several years old, or barrels that have been stored in a hot or cold location or in direct sunlight. Age or exposure to heat, cold, or sunlight can cause the rubber of the barrel to develop tiny cracks or deform.

Cracks can often be detected by tracing your finger around the sealing surface of the barrel or doing the same with a soft cloth. You might feel damage with your finger, or the soft cloth might snag. The damage might also be visible if you flex the barrel rim slightly. This problem can only be solved with a new barrel.

Rarely, a well-used barrel will develop a hole in the bottom. The hole will usually develop in the center of the base of the barrel. That is the concentrated point of friction that occurs when a barrel full of rocks is turning. The solution for this, unfortunately, is a new barrel.

We Hope You Solved Your Leak!

We hope that one of the solutions above has fixed your leaking barrel. Most of the time the leak can be fixed without spending any money.

When that isn't possible, the small cost of a new lid, lid gasket, retaining ring, or barrel nut can usually stop the leak for a small cost. A new barrel is rarely needed.

Happy Tumbling! Authors

Hobart King Hobart M. King has decades of rock tumbling experience and writes most of the articles on He has a PhD in geology and is a GIA graduate gemologist. He also writes the articles about rocks, minerals and gems on