Why and how sand got in to your pool may seem like a total mystery, but all mysteries usually have a simple and logical explanation.
The most common explanation is that you have a sand filter and are using the wrong type of sand or your filter has an internal fault causing sand to leak into the return stream.
You really need to fix this problem quickly otherwise the problem will become worse and your sand filter may not be adequately filtering the pool.
If you don’t have a sand filter the mystery deepens. It’s likely someone or something put the sand in your pool. And no, it’s not aliens!
Otherwise, the sand like substance in your pool is not sand but yellow or mustard algae. Then you have a completely different problem to solve.
Table of Contents
Why Do I Have Sand in My Pool?
You have just discovered what looks like sand at the bottom of your swimming pool.
That’s strange! How did sand get in the pool?
Where did the sand come from? There’s no sand around the pool or anywhere in the backyard.
How do you remove sand from a pool?
And is this going to happen again?
Sand Filter
The most common answer to this mystery is you have a sand filter and it is faulty.
There is a broken part inside the filter causing sand to contaminate the water.
The filter is blowing sand through the plumbing back into the pool.
How Does a Sand Filter Work?
Sand filters are simple devices using sand to capture and hold dirt and contaminant particles from the pool water.
Pool water is pumped into the top of your sand filter and falls under gravity to the bottom. The water is also drawn down under pump pressure to the bottom of the tank.
The sand traps contaminant particles resulting in clean water at the bottom of the tank. The clean water is drawn by the pump into the laterals and up the standpipe through the multiport valve back to the pool.
The laterals are tubes with very small holes that are smaller than the size of a grain of sand. They act like a filter screen that allows water to pass through but the sand and contaminant particles cannot escape and remain in the tank.
What If I Don’t Have a Sand Filter?
Well, that would be even more mysterious!
There are two options:
Sand was Placed in the Pool
Someone dropped some sand in the pool. But who would do that?
I have heard of small children scooping up sand from a sand pit and dropping it in a pool when their parents are not looking.
I have also seen ants removing sand between pavers around the pool and pushing it into the pool.
Yellow / Mustard Algae
It’s not sand but yellow or mustard algae.
If the substance is dispersed around the pool or concentrated in a few places not under the return jets it’s most likely algae.
Test the substance by trying to scoop up some of it and bring it to the surface to check it out.
Push your pool brush through the substance to check whether it keeps its state or breaks up into a cloud of fine particles. If it becomes a cloud, it’s algae.
Please refer to our article How to Get Rid of Algae in a Pool
Why is the Pool Filter Blowing Out Sand?
There are several possible reasons that your sand filter is leaking sand into the pool. The most common reason is that there may be damage inside the filter unit, especially broken laterals. However, there may be sand in your pool when the laterals are not broken.
Any of these reasons can cause sand in the pool:
Too Much Sand in the Tank
Most models of sand filter require at least 6 inches (15cm) of clearance from the top of the filter tank to the top of the sand.
(Please check the user manual for your model of sand filter)
If there is too much sand and not enough clearance the backwash and rinse cycles may be less effective than normal. During these cycles sand may be pushed back out of the tank into the plumbing pipe and into your pool.
New Sand Not Bedded Down
When a sand filter is cleaned out and filled with new sand you need to carry out the following process to eliminate fine sand granules and bed down the sand.
Firstly, set the multiport valve to backwash. Run the pump for a few minutes to backwash the new sand to remove any fine sand particles. Otherwise, these fine particles may escape through your filter into the return lines and deposit in your pool.
Secondly, set the multiport valve to rinse to bed down the sand. Run the pump for a few minutes.
Lastly, set the valve to the normal filter position. Operate your pump as normal.
Remember to never move the multiport valve while the pump is operating as it will damage the valve gasket which will cause leaks.
Wrong Type of Sand
Only use proper high grade pool filter sand in your sand filter.
Pool filter sand is a special type of sand especially designed for sand filters. The sand has sharp edges which hold on to dirt whereas other types of sand have rounded edges and don’t trap the dirt as well.
Never use any other sand as it won’t work correctly.
Broken Multiport Valve
If the multiport valve develops a problem it will need to be replaced.
You can purchase spare parts for multiport valves but usually it’s better and easier to replace the whole valve rather than try to repair an old multiport valve.
Faulty Laterals
There are 8 to 10 laterals projecting out like a starburst from the bottom of the central standpipe.
If one or more of these lateral filter pipes is damaged then sand will escape into the water and be pumped into the pool.
Faulty Standpipe
The standpipe is the vertical pipe running from the multiport valve down to the array of laterals.
This pipe is made of thick plastic but can become brittle over time developing splits, cracks or holes.
If there is a lot of sand in your pool it’s probably the standpipe that has broken or split.
Faulty Valve Gasket
A worn multiport valve gasket may allow sand and dirt from the filter tank to escape into the return pipe when backwashing or rinsing the filter.
I recommend replacing the valve gasket every time you change the sand to prevent this problem.
Replacing the multiport valve gasket is easy.
- Turn off the power to the pump.
- Release the pressure from the filter.
- Unscrew the inlet and outlet pipes.
- Unscrew the clamp holding the multiport valve on the tank
- Lift out the complete valve unit.
- The gasket is sitting inside the bottom of the multiport valve.
- Replace with a new gasket. Usually, they are glued into place.
- Reassemble the multiport valve to the tank.
- Turn on the power and test the filter.
Please refer to our article on How to Use a Pool Filter Multiport Valve
How to Fix a Broken Standpipe or Laterals
The part that tends to fail the most is the laterals but it’s common sense to replace both the standpipe and laterals as they are connected and work together. Usually, they are sold as one unit for most brands of filter.
It is not possible to find out what part is broken and needs replacement until you empty the sand from the filter tank.
Note: Please ensure you order a new standpipe and laterals before you empty your sand filter. Otherwise, you cannot repair the filter immediately.
Once you open the sand filter you can no longer filter your pool water. And the longer your filter is out of action the more likely your pool water will become contaminated and turn green.
These parts are lightweight plastic components that can be delivered to your home. The most convenient way to purchase the parts is to order online.
After replacing the faulty parts, you can reassemble your filter and turn it on again.
Replacing the standpipe and laterals is a simple process.
First, you need to follow the procedure for emptying your sand filter and replacing the sand.
Please refer to our article on How to Change Pool Filter Sand
While the filter tank is empty you can easily replace the standpipe and laterals. The fitting simply attaches into the bottom of the multiport valve.
How to Replace Sand in a Pool Filter
- Switch off the pump motor at the power supply.
- Disconnect the plumbing pipes at the multiport valve.
- Remove the multiport valve from the top of the tank.
- Remove the sand from the filter. Sometimes it’s easier to turn the tank on its side and scoop out the sand with your hands or a plastic cup.
- Remove the standpipe and laterals. The laterals fold upwards or unscrew from the standpipe.
- Hose out the tank to remove all traces of dirt and old sand.
- Replace the standpipe and laterals.
- Fill up with sand or filter balls. Don’t over fill the sand. There must be a 6-inch gap between the top of the tank and the sand.
- Reassemble the sand filter.
- Check the multiport valve gasket and replace if worn.
- Replace the multiport valve.
- Reconnect the pipes to the multiport valve.
- Switch on the power and test your filter.
- Backwash and rinse the sand.
- Check for water leaks around the tank and ensure no sand is coming out of the outlet jets into the pool.
Filter Balls for Sand Filter
You may as well replace the sand with filter balls. This is the modern upgrade for filter sand.
Are filter balls better than sand?
YES!
The advantages of Filter Balls
- Much lighter and easier to handle than heavy wet sand.
- Easy to fill and empty the filter tank.
- Easy to dispose of in the garbage.
- Filter balls can be cleaned and recycled. Wash them in the washing machine.
- Captures finer particles (down to 10 microns) than sand leaving the water crystal clear.
- Filter operates at lower pressure as water can more easily move through the filter balls than through sand.
- The pressure gauge remains low for longer resulting in less requirement to backwash the filter.
- Reduces water usage with less backwashing.
- Results in higher flow rate with strong water pressure stream at the return jets.
- Better water circulation around the pool.
- Vacuum suction pressure is strong.
- Less strain on the pump motor resulting in less filter and pump noise.
- Less strain on the whole filtration system.
- Operate the filter less hours resulting in electricity savings.
- Much less likely to have a broken standpipe and laterals with filter balls as they are not heavy and dense like sand.
- Easier to prepare your filter for winter. Water drains from the tank quickly and it’s easy to remove the filter balls. No more damp sand freezing and expanding in the filter tank causing damage.
- Easy to purchase online and have delivered as there is no weight.
- Filter balls cost less than bags of sand.
Another added use for filter balls is to drop half a dozen balls into the skimmer basket to capture dirt particles before they reach the filter. And it’s dead easy to remove them, give them a rinse and put them back in the skimmer. This works almost as well as a skimmer basket filter sock.
Read out article Pool Filter Balls Work Better Than Sand
How to Remove Sand from a Pool
Usually when a faulty sand filter blows sand into the pool it will accumulate on the bottom under the outlet jets.
The only way to remove the sand from the bottom is to manually vacuum the pool. You will need to move the vacuum head slowly so as not to stir up the sand.
I recommend using a skimmer basket filter bag to catch the sand. Leave the multiport valve set to ‘filter’.
Otherwise manually vacuum the pool with the multiport valve set to ‘waste’. The sand will be deposited in the drain and not back in the filter.
If you are going to open the filter and fix it you don’t want the sand back in the filter.
Remember this will lower the water level slightly so you will need to top up the pool with the garden hose.
Note: Automatic pool cleaners are not always useful for removing sand from the bottom of your pool.