Cat not using box

Question
I have a six year old female who rarely uses her box.
I brought her and her brother home from the Humane Society about four years ago. I gave them both brand new boxes and I feed them the same food their previous owner was feeding them.  They are inside only cats.  Her previous owner had her front feet declawed so she has her own box with pellet litter.
From DAY ONE she has taken to peeing and pooping directly infront of my front door, infront of my computer and  directly outside of the box.
I can never catch her in the act so I don't know if it is day or night or what.  When I do find it, I treat it first with a hot steamy towel and then cat urine cleaner.
I tried steam cleaning the areas the first 3-4 months she did it, but I just can't afford it every month.
I had my landlord bring out his carpet guy and that didn't do any good.
I have tried every cat urine cleaner I can find in the pet stores that I can get my hands on.
On average, she will pee and/or poop in the box 2 out of the 14 times a week she may go to the bathroom.  
I change both boxes 1-2 times a day.  Nothing in their diets have changed, nothing in the home has changed, nothing in my schedule has changed....I play with each one separately when I come home from work, give her brush outs every Sunday.....I am at my wits end.
I have taken her to the vet four times and she is perfectly healthy, but my vet really isn't giving me any new information I haven't already used before.
In the last three years, I have given her three new litter boxes.
I am paranoid about the smell and am very embarrassed.
My home is very clean and organized-BUT IT TENDS TO SMELL! What's wrong with my cat, how do I get her to stop this and how do I get the smell out and stop her going back once and for all?

Any advice is greatly appreciated!
Thank you!

Answer
Melody,

The reason you are having a problem is probably due to her being declawed and using pellet litter. When they are declawed their 'fingers' are amputated to the first knuckle so the claws don't grow back. Some cats have lifetime emotional and physical problems because of it. Some cats get ultra-sensitive nerve endings where they were declawed and scratching in a litterbox is painful. Using pellets is like not having any finger tips and digging in rocks, so she probably is avoiding the litterbox. I would try using a fine clumping litter. Or try using puppy pee-pads (so she doesn't need to dig)  next to the litterbox and see if she using those.

Here is a 'receipe' for cat urine odor removal:

1 quart of 3% hydrogen peroxide
1/4 cup baking soda
1 teaspoon of liquid soap

(3% hydrogen peroxide can be bought at most grocery and drug stores in pint and quart bottles).

Gently mix all ingredients in a non-metal container. Do not mix or shake vigorously!

The mixture is best used when fresh but can be stored. Do not keep mixture in an airtight container.  Have a VERY loose lid as baking soda and hydrogen peroxide when mixed together will release oxygen and an airtight container will explode. You can mix and keep it in large spray bottle (Home Depot, etc.) but a plastic liter or 2-liter soda bottle works just a well.

Always test for color-fastness. Hydrogen peroxide is a bleaching agent in stronger concentrations and can lighten materials that are not color-fast.
HOW TO REMOVE CAT URINE ODOR FROM CARPETS

FOR INDIVIDUAL URINE SPOTS ON CARPET:
If fresh, sop up as much cat urine as you can with a paper towel first. Use a spray bottle to saturate the spot completely with the recipe - do not blot. The recipe must penerate the padding and possibly the floor boards underneath, where the urine has penerated for it to work.

Wait 24-48 hours until dry then vacuum. If the urine odor is still present - repeat the procedure. It usually takes 2-3 applications to completely neutralize the cat urine odor.

FOR LARGE AREAS OF CARPET:
You can use a carpet cleaning machine - one of your own or a rental and use the recipe instead of the shampoo. You will have to make several gallons of the recipe depending on the size of the carpet. Don't use the vacuum part of the machine - you will want to let the solution soak and dry for 24-48 hours before vacuuming.

Please bear in mind that most carpet cleaning machines are not made for this use and baking soda can clog the nozzles of the machine - so use it at your own risk. Instead, I used a 1 gallon garden bug sprayer I bought at Home Dept for about $20.00. It worked great and if you ruin it, its not such a big expense to replace it. I had to rinse the nozzle out frequently by filling the tank with hot water and spraying it in my bathtub until the nozzle was clear but it worked!

If using the sprayer saturate the entire carpet with the recipe, let dry for about 24-48 hours and vacuum. You will have to probably repeat the procedure again. One of my bedrooms only needed 2 applications but the other 2 that where heavily saturated with old urine took 3 applications over a week.

Also, if the cat urine is old and dried, the smell will probably be worse a day or two later. This is because you are rehydrating the uric acid crystals in the urine to neutralize them. The smell will get better with each application!



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CLEANING CAT URINE FROM MATTRESSES:

For mattresses you must saturate the spot throughly to get deep down into the padding and springs to neutralize the urine. If the cat has urinated alot in one spot, the mattress can be soiled all the way to the other side! Let the area dry for 24-48 hours without bedding then reapply if necessary.

REMOVING CAT URINE ODOR FROM CLOTHING, COMFORTERS AND BEDDING:

Put the items in the washing machine and pour in enough of the recipe to cover throughly. This might take a few gallons depending on the size of the load. Soak for at least 24 hours, rinse and then rewash using normal washing detergent. If any of the odor is still present, soak again for 24 hours, rinse and rewash.

A small area on a comforter can be spot treated by saturating the area throughly, letting it dry for 24 hours, then washing the comforter normally in the washer with detergent.
Always check for color-fastness before using.

I hope this helps.

Tabbi