Last summer we made the decision to get a pool, the small inflatable pools were just not cutting it in our hilly yard so we decided to get something a little closer to permanent. We are a family of 4 living on one income so when we encountered the $79 on sale Summer Escapes 12' x 26" above ground pool, we jumped on the opportunity. My wife's family followed suit, it is a great deal for a little summer fun (especially with two toddlers), enough water for mommy and daddy to get in, yet shallow enough that our one year old is able to stand on the bottom.

Everything was going great for about three weeks, then it started, the water started to get a little cloudy then green, we had the chemicals right, the filter just couldn't keep up. The filter itself is not much more than a slightly oversize aquarium filter. The pump, strainer, filter cartridge and chlorine holder are all in one unit. It is just not able to keep up. The only way we were able to keep the water swim worthy was to change it out about once every three weeks, water is expensive, this wasn't going to work.

I was ready to give up and take it to the dump this spring. My in-laws were ready to do the same and offered to let us have all of their parts including their clean liner and larger filter from their old pool that wasn't a direct replacement. I gathered my tools and my two apprentices and got to work making it fit.

Note: Your materials/tools may vary slightly depending on your filter/pool model.

Materials:
1 - 1.25" Bulkhead union
1 - 2" x 1.5" flexible PVC coupling
Intex pool filter kit
2 - pieces of 2x lumber approximately 6" longer than the diameter of the filter's widest point.

Tools:
Drill
Chisel
Utility knife
Flat screw driver
1.25" hole saw
2 x pliers (slip joint, oil filter)
Sheet metal snips (optional)
2 x Bar clamps (at least 3" longer than the filter housing is tall)

Disclaimer: using power tools is inherently dangerous, please be sure to educate yourself on the dangers and proper methods for their use. Always wear proper safety equipment and be sure to keep your children safe as well. Performing this modification will most likely void your warranty and is not reversible once you start cutting, you have been warned. Modify at your own risk, be sure you understand the risks involved in cutting/modifying a vessel holding thousands of pounds of water, you are responsible for any damage or injury that may be occur.

Step 1: Remove Filter From Pool.

a. The filter on this model is held on with 10 metric self tapping screws. Take note of how the filter is assembled.
b. Remove stkimmer basket and any filter cartridge.
c. Disconnect the outlet hose and diffuser.
d. Remove the undersized pump from the bottom of the filter.
e. Thoroughly clean and dry the housing (unless you want green slime spread across your work area).

Step 2: Enlarge the Pump Hole.

a. The first image shows the "exploded view" of the upgrade. Left to right: new filter hose, flexible coupler, bulk head union, filter housing.
b. Trim the ribs and locking elements flush with the outer ring on the bottom of the filter housing.
c. Using the hole saw, cut a hole near the center of one of your 2x boards.
d. Center the hole in the board with the hole in the bottom of the filter. Use the second board to span the top of the filter housing and secure the two using the bar clamps.
e. Using the hole in the board as a guide for the hole saw, slowly cut the hole in the filter with the drill slowly in REVERSE. This prevents the teeth of the hole saw from grabbing the plastic and tearing the drill from your hands. This will only work with a hole saw that has a lock in addition to the threaded mounting point.

Step 3: Create a Flat Surface.

Using a SHARP chisel (you should be able to use the cutting edge as a mirror or it isn't sharp), pare away the remaining ribs, leaving the outer ring rib.
Pro-tip: Cutting in this situation you will have the most depth control by cutting with the bevel down. Always cut away from your self and brace your tool hand to prevent slipping and cutting more than you intend.

Step 4: Install Bulkhead Union.

a. Disassemble the union (note: threads are left handed), depending on the model, you will have 3 or 4 parts:
1 x male threaded inner peace
1 x nylon/UHMW/HDPE washer (some kits do not have this)
1 x EPDM gasket
1 x hex nut

b. Starting with the male threaded piece, install the gasket, then insert the threaded portion from the inside of the skimmer housing.

c. Install the plastic washer and then the nut. Tighten hand tight and make sure everything is lined up properly and the gasket is flat and centered.

d. Using the pliers grasp the nut and the hex portion on the end of the male threaded part. The object when tightening is to limit the rotation of the parts in contact with the gasket, only turn the nut. The consequences of turning the other pieces may be a torn, disfigured gasket ready to fail.

Pro-tip: oil filter pliers open much farther than equivalent sized slip joint pliers.

e. Test the seal by holding your hand over the opening and fill with water, watching for leaks.

Step 5: Modify the Hose to Fit the Coupling.

Note the hose end on the left, this is what it looks like before modification.

a. Starting with the snips, remove a majority of the flange on one end of the hose (other end will connect to the filter) and remove the coupling nut.

b. Using the utility knife, pare the last of the flange flush with the hose end (see hose on right)

Step 6: Connect Hose to Skimmer Housing.

Connect the hose end to the external threads of the union using the flexible coupling.
A socket/ratchet or nut driver may be substituted for the flat scree driver for a more efficient installation.

Step 7: Re-install Skimmer Housing to the Pool.

Recalling the way in which the skimmer housing was installed originally, re-install the skimmer, the strainer and the associated parts. If your filter included a cartridge in the housing, do not install it, the new external filter will contain the cartridge (or sand if you are lucky enough to find a sand filter).

Step 8: Reinstall the Outlet Hose.

a. The new filter likely includes a larger outlet fitting. Using the nut as a stencil, draw the new required opening centered on the original hole. Make sure the new hole does not extend beyond the reinforced area surrounding the hole (if it does, you may need to modify the original outlet to work with the new filter). In my case, I had a good 2 inches around the hole and I only needed to increase the hole by about .75" in diameter.

b. Using the snips or heavy duty scissors cut the hole larger.

c. Install the new outlet fitting in the newly enlarged hole according to the instructions provided with the filter.

d. Connect the hose to the fitting.

Step 9: Connect the New Filter.

a. Connect the new filter, the hose from the skimmer to the "in" port of the filter and the outlet hose to the "out" port.

b. Fill the pool to the prescribed level and check for obvious leaks.

c. Plug in your filter and check for leaks one more time. If you find any, they will most likely be where the bulkhead union passes through the bottom of skimmer or around the flexible coupling. Tightening the fittings will usually fix the issue.