The most likely culprit for smells next to a bathroom is mold from the water damage behind the walls due to a slow leak or a improperly waterproofed shower or tub/shower. The solution is not to attempt a bandaid. It's to find the source of the problem and fix it. That will mean ripping out walls or floors and isn't simple.

I have a cat that does the same thing in our master shower. She's 17 though and just doesn't want to travel the 100 foot distance from the master to the litter box located in the utility room. We put a litter box in the master, and she used it, but it and the litter box "shakeoffs" got in our way. So we resigned ourself to living with cat pee in the drain in the shower.

Frequent flushing of the drain with water will carry the urine through the pipes away from the drains. If you don't flush water through it, it collects in the P trap and will start to smell. A frequently used shower shouldn't really have this issue because the P trap is being flushed out. If your tub is infrequently used, take a couple of cleaned out milk jugs and fill with tap water and a couple of table spoons of baking soda and use that to pour down the drain several times a day. The reason I suggest that rather than just turning on the tub to flush it is the other water infiltration issue that you are dealing with. It could be coming from the drain, but it's most likely coming from the supply end, or from the shower not being adequately waterproof.

You need to eliminate the source of the smell. Has the water heater been inspected? If it's not leaking and causing mold or mildew, it could have other problems like buildup of hard water residue which can smell funny when heated in the hot water tank.

Cats urinate outside the box 99% of the time due to medical problems. I'm not "lecturing" but I do want you to be aware that cats generally seek out cool, smooth bathtubs when they experience burning pain when urinating, due to an infection, crystals or ideopathic urinary tract inflammation.

If you feed your cat any dry food, eliminate the dry food and feed only wet food. Wet food is the only way to keep a cat properly hydrated - no cat can possibly drink enough water to compensate for eating dry food. Imagine eating dry cereal with no milk on it for every meal. Getting enough water into the diet will increase urination frequency and dilute the urine, reducing the chance of bacteria growing in it and crystals forming in it.

BTW my cats are 19 and 18 years old and use the litter box consistently. They are fed a high moisture raw meat diet.

To eliminate the smell in the drain, get an enzyme cleaner from the pet store meant for cat urine and pour it generously down the drain, allow to sit overnight before using the tub/shower. Bonus is the enzyme cleaner will help clean out other gunk from the drain without harming the environment or your pipes and leave the drain smelling fresh. (Works great for garbage disposals too)

http://www.catinfo.org./?link=urinarytracthealth

I will change his food. I guess even the high priced stuff can cause problems at times. As far as the bathroom goes, I have installed a new water heater twice in the past five years and no leaks were found. I have removed the sheetrock between the closet and the bathroom and the smell is still there. I mentioned the cat because everything I use in the tub to flush and clean it really smells strong in the bedroom too. While it would make sense that this is due to some missing sheetrock, I did not remove the cement board surrounding the tub so there is still substantial wall between the two. When you say waterproofed what exactly does that mean? I am trying to do as much as I can myself simply because I have spent so much on repairs elsewhere I just don't have money to keep hiring people. just had the house completely re-plumbed due to constant pipe breakage. Just in past month have had running water after a year and a half without. (Had to rent a house while trying to get all that done). Would I need to remove the tub completely to check for proper sealing? It is a very old cast iron job and sealed in on three sides. Thanks so much for the responses!

A couple of other things I forgot are that this smell was here when I bought the house. I thought it was just old carpet--nope. I have removed all flooring in the entire house. Also my sweet kitty has done this since the first week we brought him home at 12 weeks of age. Vet said the kitties were probably box trained in a tub so he sees it as part of a litter box. But the part about eating dry cereal with no milk got to me. I have tried wet food with him several times and he just doesn't seem to like it but I'll give it another try. It's worth a try to maybe decrease the smell. I did try one of those electric self-scooping boxes but he is so big he went too much and it kept locking up. Now they put a weight limit on them, which him being a Ragdoll, he is too large for them He did go in it as long as it lasted. Sure wish they'd increase the size of those. Lol. I'm thinking I may tear out the little closet that is between the tub and the water heater and see what's going on there. Everything is built in-no premade cabinets in this old house so they are difficult to remove--especially in the limited space. Also, GREAT suggestion on the enzyme cleaner. Will head to town tomorrow to get some. Has anyone heard of the Odoban products? I was wondering if using it on the wood framework before putting the sheetrock back up would seal in any smell that may be hiding in the wood. I just don't see me tearing down studs.

You say,

A couple of other things I forgot are that this smell was here when I bought the house

I would be interested to know the location of your vent line, a small leak would tend to manifest itself in some of the odors you describe.

I really wonder about leaks in the tub drain, the smell should wash away when you flush water down there. It could be some slow leaking around the drain causing mildew and smells under the tub and in the walls. Can you replace the tub drain pipe, or at least the drain flange?

For the cat diet change, try a raw frozen or freeze dried (you just add water at meal time) diet. Stella and Chewy's is a good one. One of my cats never liked canned food but when I switched them to raw 8 years ago he liked it fine. I make home made as it's best quality and also less expensive than buying the premade stuff, but to try it out you can buy it at most pet stores and online. I use a recipe similar to Dr Pierson's on that website.

I was wondering about the vent stack too. It would make no sense that the cat urine going down the drain should cause a smell. In my opinion the tub drain would be a perfect place for a cat to pee :) It is washed down the drain and away. I am not a plumber but I know that vent stacks are hidden in walls and maybe yours could be cracked. There is only air to go through the stack, so if cracked you wouldn't have any visible sign.

I was going to ask also, how often do you use the tub? Maybe the water has desolved out of the trap and that lets sewer gas (odor) come up through the stopper. Pour water and maybe cloryx down the drain and see if the smell goes away.....then make sure water goes down the drain every week or so.

In addition to leaks, an improperly vented sink or tub trap would cause odors. So would a blocked vent stack. Look for a birds nest before tearing the house up.

I attributed the endlessly stinky bathroom in a rental I owned to the five co-eds sharing it. When they moved and I gutted the room, the plumber found the vent terminated in the wall--never even went to the roof.

As above, check the vent first.

Some cats see a hole and use it. Be glad it's not the kitchen sink. I think a cat using a drain is quite civilized!

If the smell is cat pee, you know it. Nothing smells like that (except maybe boxwood).

Actually some types of mold smell like cat pee, which is why a leak is a possibility as well. Juniper bushes, too!

Juniper bushes smell like cat pee because cats love to pee on them, as well as the tires of my truck!

I love when someone comes here, asks a question and then disappears, usually new members that forgot where the site is or lost password.