Backwashing is crucial for keeping your DE (diatomaceous earth) filter in good working condition. As the filter traps dirt and other contaminants, it will clog over time, meaning its efficiency reduces significantly and hence the need to backwash.
While backwashing will help restore the efficiency of your DE filters, it will also wash away most of the DE powder. Therefore, you have to add more powder after backwashing, and it is essential to know how much you will need to plan in advance.
Remember that adding too much DE powder can break down the filter, while too little means it will not effectively clean your pool water.
When to Backwash a DE Filter
The frequency of backwashing your DE filter depends on how you use the pool. Heavy usage swimming pools require more frequent backwashing as contaminants accumulate in the filter within a shorter time.
That said, most filters will require backwashing at least once every 1 to 3 months. A good way to tell when to backwash your filter is by checking your pressure gauge. If the pressure increases by a few PSI, you need to backwash the filter as it means water is not flowing smoothly through the filters.
There are some other special instances when you might need to backwash your DE filters. Key among them is when dealing with an algae bloom as a lot of it is trapped on the filters. Also, make sure you backwash after inclement weather, such as rainstorms, as they often add high amounts of dirt and debris to the pool water.
How Much DE Should I Add After the Backwash?
The amount of DE you have to add after a backwash depends on what you will lose as you wash out the filters. However, it is not always easy to calculate how much the filter loses as you would have to remove the filters and measure the amount of powder still on the grids.
In most instances, you will need to add about 80% of the DE powder you would add to a new filter. Backwashing will not remove all the powder from the filter, as some will cling to the grids.
DE filter manufacturers often provide clear directions on the amount of powder you need to add to your new filter. If this information is not available, the rule of thumb is to use 1 pound for every 10 square feet of the filter.
Therefore, if you have a 60 square foot DE filter, you need around 6 pounds to fill up a new filter. However, if you are backwashing the filter, you will need to add just 80% (4.8 pounds) of this afterward.
Another easy way to tell when you have added enough DE powder to your filter is by monitoring the pressure gauge. Keep adding the powder until your gauge hits the normal pressure, which is between 10 and 13 PSI for most swimming pools.
How Do You Measure DE Power?
A DE scoop provides the easiest and most accurate way to measure your DE powder when refilling your filters.
One scoop holds around 0.5 pounds of the powder. If you are refilling your 60 square foot filter after a backwash, you will need 10 scoops, which is about 5 pounds of powder. However, the last scoop should be a little over half full, given you need 4.8 pounds.
Most pool supply stores will stock DE scoops, so you should not have any difficulties finding one. If you cannot find a DE scoop, you can still use other things at home to measure the powder. One of the best ones is a 1-pound coffee can, as it holds the same amount of DE powder as a DE scoop.
Also, you can use a standard measuring cup. 6 cups make a pound of DE power. Therefore, if you need 5 pounds to refill your filter, you have to add 30 cups of the powder. However, you can make the job easier by using measuring cups with a larger capacity, such as 4 or 6-cup ones.
How to Add DE Powder
Another crucial thing you have to know when refilling your DE filter after a backwash is how to do the job correctly. However, this only requires you to follow the steps below.
Step 1: Switch Off Filter Pump
Once you finish backwashing, you have to switch off the filter pump to start the process of refilling the DE powder.
Switching of the pump allows the dirty water from the backwashing to drain out. Also, make sure you open the air relief valve and drain plug.
Step 2: Open up the Filter and Remove Grids
Next, you need to open the filter and remove the manifold piece to take out the grids. Some filter types will use a spring clamp closure that is easy to take apart, while others require you to unscrew bolts or screws, which takes more effort and time as you need to use tools.
Step 3: Rinse the Grids and Return Them to the Tank
To remove the grids, you have to take out the inside manifold piece. Ensure you rinse the grids well with a garden hose as there will be some contaminants and DE power clinging to them.
Also, remember to rinse the inside of the tank, after which you can return the grids and manifold to the tank while making sure you put them back to their correct positions.
Step 4: Prime the Pump
It is crucial to prime the pump before adding the DE powder. Here you should add some water to the basket, close the lid tightly and switch on the pump and make sure you give it enough time to prime.
Step 5: Close Relief valve
Once you are sure there is air in the tank, you can close the air relief valve. You can tell when it is time to close the air relief valve when you see a steady stream of water shooting out, which is an indication there is no air in there.
Step 6: Add DE Powder
Now it is time to add the DE powder you measured before. It is best to add it to the skimmer basket closest to your pump and filtration system.
Start by removing the skimmer cover and then pour in the powder slowly, and make sure you do not just dump all of it in as this will clog the pipes.
Note: Make sure you wear a mask when handling DE powder as you do not want to breathe in some as it can cause severe health issues.
Step 7: Check Air Pressure
The last step is to check the air pressure gauge, even if you have been watching the pressure when adding the DE powder.
Checking the gauge one more time after the job allows you to determine whether you have added enough DE powder. If it is at the normal operating level (about 10 to 13 PSI), you have enough DE powder, and the job is over.
DE powder is crucial for your filtration system's functioning, so you need to restore it to an optimal level after backwashing.
Backwashing removes around 80% of the DE powder, and so that is just what you will need to add as anything more or less than this can cause problems.
If you know how much your filter holds or even just the size, it should be easy to figure out how much powder you need. Also, make sure you measure it accurately with a DE scoop and follow the steps above to add it correctly.