Sand Filter Leaking from Flange Clamp – 3 Main Reasons of Leakage and 4 Simple Solutions


pool sand filter leaks from flange clamp

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Recently I was researching about the pool sand filters and I found one interesting report about it.

As per the research report published on, the market size for pool sand filters is increasing rapidly all across the globe.

It also states that it will reach a significant market share by 2028.

Pool sand filters are indeed one of the most widely used pool filters across the globe.

They are easy to handle and their maintenance is pocket friendly too.

At the same time, these sand filters are quite efficient in their overall functioning.

All these attributes make them very popular among swimming pool owners.

The working principle of a sand filter is also very simple.

Here, the sand plays the main role in the filtration process. 

In this device, a tank of specialized sand is inserted in the pool filtration medium.

Pool water with dirt and debris is passed through this sand.

The sharp edges of the sand help to remove the impurities from the pool water when passed at a high speed.

After that, the clean water flows back to the pool and the impurities are removed from the pool water.

Generally, sand filters are durable and reliable in their functioning.

If you use and maintain it properly, it can last up to 3 to 7 years without replacement.

But again, like all other devices, pool sand filters are also prone to faults and malfunctions if not taken care properly.

One of the most common problems faced by users while operating sand pool filters is leaking from its flange clamp.

Although it may seem simple, these leaks can seriously affect the overall performance of your pool sand filters.

The main purpose of the clamp in the sand filters is to secure its various parts and prevent the occurrence of leakage and any loose connection.

The body of the clamps is commonly made from metals or plastic.

But its jaws are also always curved out of metals. It is because metallic jaws provide a strong and durable grip.

In a sand filter, the flange clamps are found with the multiport valve (MPV).

The multiport valve is a very important tool in the sand filter.

It is fitted with the filter tank flange with the help of clamps and sealed with the O-rings.

As the name suggests, MPV has more than one port.

The MPV found in sand filters generally has three ports namely the pump port, the return port, and the waste port.

The pump port receives the pool water with dirt and debris.

The function of the return port is to divert the flow of clean water back to the swimming pool.

The waste port is responsible for directing the water during the backwashing operation.

Now a leak in the flange clamp means the connection between the MPV and the filter tank has loosened or destabilized.

If such a situation occurs, it will directly affect the entire operation and performance of the sand filters.

So, a leak in the flange clamp should not be taken lightly and should be fixed immediately.

Let us dig deeper and understand why the flange clamp of the sand filter leaks and what you can do to fix this problem at its source.

3 Main Reasons for Sand Filter Leakage at Flange Clamp

If there is a leak at the flange clamp, the following issues may be the main culprits.

Reason 1: Loose Connection of the Flange Clamp

As mentioned earlier, the MPV is connected to the pool filter tank flange with the help of clamps.

Sometimes, the daily operation of the device may impact the flange clamp connection.

The grip of the clamp may become loose after some days.

It can cause the water flowing in and out of the MPV to leak.

So, when you observe the flange clamp leaking, you should at once check the connection of the flange clamp with the MPV.

Reason 2: Dirt and Debris inside O-rings of Flange Clamp

The main function of the O-rings in a sand filter is to seal the clamp band.

In the case of the flange clamp, it does the same job.

It helps to seal and secure the connection of the clamp with the tank flange.

This action makes the bond between the flange clamp attaching the MPV with the filter tank much stronger.

In addition to this, it prevents MPV from slipping.

But in due course of time, particles like dirt, sand, pebbles, and other impurities enter inside the O-ring.

This gradually weakens the sealing capacity of the O-rings and may cause the flange clamp to leak.

Reason 3: Flange Clamp Bolt Gets Stripped or Loosened

In the sand pool filter, a circular-shaped clamp is used.

They are also called marman clamps.

This type of clamp looks like a band with a gap between them.

A bolt is present in this gap.

Using this bolt, users can tighten or loosen the grip of the clamp.

But due to external reasons like differences in thermal expansion of materials, vibration, shock, etc, this bolt may get loosened or stripped.

In such cases, the flange clamp grip will become loose resulting in the leakage of the sand filter.

You can also check out the following video to understand these reasons of leakage in more detail.

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4 Solutions to Fix a Leaking Flange Clamp of a Sand Filter

If you ask me then I would tell you that fixing a leaking flange clamp is not that difficult task.

But before you start fixing, you must first understand the cause of the fault.

This is because the repair method is different for each problem.

If you know the reason, the troubleshooting part becomes simple.

Here are 4 easy solutions to fix a flange clamp leak for the sand filter.

Solution 1: Tighten the Loose Connection of Flange Clamp

If a loose clamp connection is the cause of the leakage, then you need to tighten it for sure.

For this, you have to remove the clamp and reattach it more securely.

Once you tighten the clamp connection, observe if the leaking issue is still there.

If there is none then you are ready to use your sand pool filter again.

Solution 2: Remove Dirt and Debris from O-Rings

If the presence of dirt and debris in the O-rings has caused the leakage, you have to remove it carefully.

Once the cleaning is over, do not forget to lubricate the O-ring with a silicon-based lubricant like Super Lube.

It helps to enhance the durability of the O-rings and enhances their performance.

Solution 3: Use Rubber Mallet for Tightening the Connection

In case the problem still persists, then you will need a rubber mallet to fix this issue.

You need to tap around the circumference of the filter and slightly tighten the connection.

This will help to fix the leaking problem at flange clamp.

Solution 4: Replace the Clamp Assembly

After applying all the above solutions, if the leaking problem still continues then you will need to replace the clamp assembly.

If the flange clamp is leaking due to a stripped bolt, the only solution is the replacement of the clamp assembly.

Here you need to remember that clamp assembly fittings for every pool filter model are different.

In other words, clamp fittings are model specific.

So, while purchasing, you need to always confirm the compatibility of your device with the clamp assembly.

While fixing the new clamp assembly, you must not leave gaps between the springs.

Also, the use of washers and adhesive patches reduces the chance of clamp bolts being stripped off.

I recommend you to watch the following short tutorial video where you will exactly learn how to replace the clamp assembly successfully.


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