Making a wet bag to fit a particular container

I've really been getting tired of washing out my diaper pails so I decided to make some PUL diaper pail wet bags. That way I can just throw the wet bag into the wash with the diapers and only wash the actual pail, once and a while. The containers I use for diaper pails are actually used Milkbone containers. We don't have a dog but I collected a whole bunch from my friend Tara. Really anything can be a diaper pail that is plastic and has a lid that fits securely.
In order to find the size of the bottom of your wet bag, trace the bottom of the container onto thick paper or cardboard (using a paper bag is great).

My diaper pail actually gets bigger going from bottom to top but I really didn't feel like figuring out the difference in the sizes and then how to make the sides so that they fit on the slight diagonal....so I just traced the larger size (the top) and therefore the wet bag will be a bit bunchy inside (no big deal!).

Take the tracing and add 1/2" all the way around so that the top of the wet bag will fold over the top of the diaper pail and be easy to take on and off.

Hint: Use a quilter's ruler (it's clear) and line it up with the straight part of the tracing.
In order to add rounded corners to your larger pattern you could just free-hand-it or you can use something round like a Tupperware cup and line it up with the sides of the pattern.
Here is my final pattern for the bottom of the pail cut out. In order to find out how much PUL is needed for the sides of the wet bag take a string and run it all the way around the outside of the pattern. Keep your finger pinching the string where it met up with the beginning and measure the length of string with your ruler. This is the exact size of the bottom of the pail. Now take that value and add 1/2" (2 X 1/4" seam allowances).

For example: My bottom pattern measured at 41 1/4" around but the final width of PUL that I cut for the sides of the wet bag was 41 3/4".
Measure from top to bottom of the pail to find out how deep to make the wet bag. Add 3 " to account for the 1/4" seam allowance for sewing the sides to the bottom, the drawstring/elastic casing, and enough fabric for the bag to fold over the pail.

For example: I measured the pail to be 15" but I cut my PUL 19" deep. Therefore, I cut a piece of PUL that was 41 3/4" x 19" for the sides of the wet bag.
Cut out the bottom pattern by laying it on the PUL, tracing around, and cutting.

Hint: Lay a book on top of the pattern to ensure it does not shift while tracing.

To cut the larger piece of PUL, for the sides of the wet bag, lay the PUL on the ground and flatten it out, smooth out any wrinkles. Line up your quilter's ruler with the uncut edge since you know this is perfectly straight. Measure and draw the large rectangle right onto the PUL and cut it out.
Take the large rectangle and fold it with right sides together. Sew a straight stitch seam with a 1/4" seam allowance. DO NOT sew the last 3" of the seam. See making a wet bag for the explanation and ironing technique.

Hint: Generally the shiny side of PUL is the "wrong" side but if you are making this bag to be strictly a diaper pail wet bag you might want to make the PUL the right side so that the seams are hidden when the bag is in the pail. I didn't do this in case I wanted to use the wet bag for other purposes in the future.
Now that you have ironed your opening you can fold over the raw edge by 1" to form the drawstring casing. Pin and sew with a straight stitch.

After stitching around, feed in the drawstring and place a toggle on the end. See making a wet bag for the explanation.

Hint: you might want to feed through an elastic so that the wet bag can just hug the opening of the pail if you don't plan on using this bag for anything else.

Hint: You could fold under the raw edge so that it is hidden but I didn't bother to do this with this wet bag (PUL doesn't fray so it doesn't make a difference). If you do fold under the raw edge you might want to add 1/4" to the depth of the wet bag to account for this.
In order to pin the bottom to the sides of the bag, first fold the bottom PUL piece in half and mark the halfway point (not shown). With right sides together, line up the middle marking with the vertical seam up the side of the wet bag (this is so the bottom is centered properly).

Pin all the way around, use lots of pins, especially at the corners. You may have to fiddle with it a bit to get the sides to be evenly distributed all the way around but keep fiddling until the sides lay flat with very little bunching. Now sew all the way around, with a 1/4" seam allowance and a straight stitch; go slow and watch to prevent puckering.

Hint: You might want to reinforce this seam by sewing another straight stitch seam 1/8" outside of the original seam (on the seam allowance).
Here is the inside of the finished bag.
And here is the outside.
Here is the bag inside the diaper pail.

You can use these instructions to make a wet bag for any shape of container, really the pattern of the bottom piece determines the shape of the wet bag. If the pail has a round bottom the bottom pattern piece will be round and the sides will be sewn from a similar rectangle as with this diaper pail.