There are a few parts to this tutorial which covers manually cleaning and then fixing or patching the grid in your diatomaceous earth (DE) pool filter.
Just back-washing your filter is not enough to keep it clean and functioning properly. Depending on how much your pool gets used and how often you get algae growth or other fine contaminates your DE filter grid (that mesh that holds the diatomaceous earth inside the filter tank) can become crusted with a “cake” like substance that is not removed during back-washing. Symptoms of this include your filter pressure increasing VERY quickly after back-backwashing and vacuuming your pool. A properly cleaned filter should be able to go a few weeks without needing to be backwashed. (For those that dont know, you must backwash your DE filter when its PSI pressure raises 10-15 PSI above where it is immediately after back-washing. In this tutorial I will show you how you can easily clean off this caked on crust to have your filter running good as new.
The other problem people have is that their DE filter gets holes in it. This can easily happen if you ever run your pump without both of the basket filters in place, which would allow for something like a piece of wood or acorn to get through and press against the DE filter grid / mesh and potentially tear a hole in it. Symptoms of this include having dirty water come back through your returns or pool jets during vacuuming.
Having just recently bought a house with a pool, I have had the opportunity to repair a very distressed DE filter and have taken pictures of the entire process to show you here so that you can repair and clean your own. A new DE filter grid costs over $150 in most cases, and usually the old ones can EASILY be cleaned and repaired. Just one new DE Filter Grid Fin can cost over $25.00.
I show you how you can make your entire DE filter work like new for less than $10.00!
So Lets Get To It!
DE Filter Cleaning
In this section I will show you with pictures how to clean the caked on crud and crust off of your DE filter. This caked on crud is the result of filtering very large amounts of algae. If your algae is not dead while you run your filter, it will continue to grow on and in your DE filter mesh and create this hard almost concrete like crusting. After years it can completely block up your filter and render it practically useless.
The first step involved is the dis-assembly of your filter tank. PLEASE read your filters instruction guide. Improper assembly and dis-assembly can lead to serious injury when you start your pump. Your DE Filter has enough pressure that it could blow its lid straight through the roof of your pool house, which could easily kill you. Make sure you exactly follow the instructions in your pool filter manual during this step.
Here is a link to the manual for my specific pool filter. My filters instructions may be different than yours. http://www.pentairpool.com/pdfs/FNSOM.pdf
Now you must remove the DE filter grid from the fiberglass tank housing. Mine lifted straight out with some force, some have threaded rods that run through to the top of the grid that must be unscrewed removed. Keep in mind, this can become extremely heavy depending on the amount of water still in, and the amount of caked on crust that is stuck to the DE filter grid. Also, the fitting of the DE filter grid to the return PVC pipe may be tight so some wiggling action may be required. Do not do anything which may crack any plastic or damage the fiberglass. Cracking the tank and causing structural problems can be extremely dangerous when you start the filter. Don’t worry, its still pretty hard to damage, just be aware.
You may want to hose it off first as it is normal for a ton of sand and diatomaceous earth to be sitting on top of the filter, even after backwashing several times. There should be drain you can open in the bottom of your tank to allow you to do this.
Again, this whole apparatus lifted straight up and out for me with some wiggling. I believe it probably weighted about 35-40lbs with all of the caked on crust stuck to it.
After having removed the DE filter grid from the tank, its time to take a hose to it to clean off as much of the caked on dead algae and diatomaceous earth as possible. You can actually hit this with a pretty hard stream of water with your garden hose attachment with out damaging the grid. I could put my hose nozzle on full blast and everything was fine. You will probably be surprised at just how much caked on crap comes off. Some guides online tell you that you need to completely dis-assemble this grid into its 7-10 individual mesh fins, however, I found that I could remove about 90% of the crust with it still intact and I did not need to take it apart. Taking it apart also risks damaging it more. DO NOT set it on its side as something like a stick or acorn or rock could punch a hole in the grid mesh. Also be delicate as the grid’s structure is made up of a skeleton or rib-cage like plastic PVC structure which is susceptible to damage if you were to drop it.
Please take note of the next 2 pictures. The first picture is before I started any cleaning with the hose. The next picture is after I have removed about 50% of the crust from the filter mesh. As you can see, there is a VERY noticeable difference in color.
WARNING – Diatomaceous earth is carcinogenic if inhaled. Please check your local laws for how this needs to be disposed of. In my area I can just hose it off anywhere, but some neighborhoods in warm climates where a LOT of people have these filters have rules in place.
After Some Hosing:
As you can see, there is a HUGE difference in color from the crusted areas and the clean areas. Its no wonder that the filter was getting clogged so quickly when I added new DE and started vacuuming. Before I started hosing off the filter grid, only about 10% of my filter was un-caked and actually capable of filtering.
Remember that you cant just do the outside, attempt to clean the insides and inside all of the cracks, nooks and crannys to that you can get as much of the crud off as possible.
Soaking your DE filter in a chemical bath: (I actually forgot to take pictures of this part.) Now that you have finished cleaning off the crust, you might notice that the entire grid seems slimy and greasy. This is probably excrement from algae and the oils will cause your grid mesh to clog easily. Also, there may be an excess build up of microscopic calcium in your mesh further impeding its ability to pass water. Get a large trash can which can hold your entire DE grid and clean and rinse it out. Use Mr. Clean and dishwasher soap to get rid of the oils and break down the calcium as well. Bleach or Liquid Chlorine will not work on this stuff. As a second step if you feel like Mr. Clean was unable to remove all the calcium, you will want to soak the grid in a bath of diluted muriatic acid over night which will clean the calcium deposits out very effectively. Make sure you dilute this properly. Full strength muriatic acid can eat right through certain materials. WARNING – Muriatic acid is VERY hazardous and can cause severe chemical burns. Use utmost caution when handling the substance.
The next day you can empty the trash can and rinse the soap or acid out of your grid (Mr. Clean worked fine for me, I did not use the acid). Do not empty this into your pool!
You have now completed the cleaning portion of this guide. If you thoroughly inspected your filter grid and did not find any holes, you may re-assemble your filter according to the manufacturers instructions.
REPAIRING your DE Filter
On the other hand, if you have found holes or tares in your DE filter grid mesh, this section of the guide will help you to repair the problem. IF you have dirty water passing back through your pool jets or “returns” while you are vacuuming, you probably have one or more holes somewhere in your DE grid mesh. I will show you in a few easy steps how you can patch these holes to easily withstand back washing for at least your entire summer season. I have successfully repaired and back-washed my pool with these patches about 10 times, and after re-checking my work, they are still holding up like brand new and show no signs of deterioration.
Buy the stuff you need for the repair - This stuff called “Water Weld” is ingenious. It is a putty that sets as hard as concrete after 60 minutes, and best of all, its completely waterproof and can even continue to harden under water. The other stuff you will need is regular old hot glue.
Locate all of the holes that you may have in your DE filter grid mesh. For me, I had quite a few up around near where the pipes connect. Damage may be easier to spot if you can disassemble your entire grid, however, I was able to patch all of my holes without doing that.
Here is what my hole looked like. It looks like someone tried to patch the mesh with silicon probably years ago and the silicon gave out. Obviously this allows dirty water to come back through the jets when you are vacuuming and these holes need to be plugged.
Fill the holes with your hot glue gun. This will create a flexible layer of sealant which absorbs into the mesh and will also give the water weld something to bond to over the hole.
That wasn’t the best picture, however you can see that the the glue has completely smothered the area.
Now its time to break out the water weld. This putty comes in a tube, and there are two putties rolled together. When you mash the putty and combine the two, they start to harden in minutes, but you will have plenty of time to apply it where you need it. Mold the putty over the areas where you have had holes to create a comprehensive shell which will protect the glue seal. Push it into the mesh and make sure to build it up around the plastic area as well.
You should attempt to do both the gluing and the water welding after the filter has completely dried. You should let the water weld cure for at least an hour before attempting to put the filter back in the filter housing and running the pump.
This is another image of a place I have welded, after several back-washes I wanted to check on the status of the water weld. I was worried it would have broken apart or disintegrated with the pressure, however it was in absolute perfect condition. I have a lot of confidence in this fix. It is still hard as a rock. I’d estimate that this will at least get you through a year. Before you open your pool every year you may want to re-apply it if you feel it is deteriorating.
You are now ready to completely re-assemble your filter, fire up your pump and add your new diatomaceous earth filter media. Remember to follow your manufacturers assembly instructions exactly in order to avoid serious injury or death. You’ve just completely cleaned and repaired your pool filter over a weekend and for less than $10.00. Congratulations.
Let me know if you have any questions or comments about this procedure! Let me know if it helped you! Don’t forget to share this with everyone you might know that has a pool to help save them money as well!
UPDATE: It’s been a year and my water weld patches are still holding strong… however, my grids are starting to tear in other locations now to the point where they definitely need to be replaced. About 3 of the grids have large vertical tares and it wouldn’t make sense to try and patch them anymore. I’d go through probably 2 sticks of water weld. But I was at least glad to get another season out of these!