I need to change the wax ring on my toilet. The closet bolts that hold it in place are rusted so I need to cut them in order to remove the nuts.
I thought of trying bolt cutters. The bolt cutters I have are, I believe, 24 inches, but they are too big to fit into the space I need to fit them in order to cut the bolts.
What is the smallest size of bolt cutters that can reliably cut those closet bolts holding down the toilet to the floor? Or is there another tool I can use?
Bolt cutters are not really the best tool for cutting off rusted closet bolts. I usually use a "mini-hack" saw:
I would caution against using any bolt cutters on the toilet hold down bolts. The reason being that they typically will apply a significant pressure against the porcelain base of the stool and crack or break it.
Another thing to consider is that bolt cutters typically have a jaw profile as shown below. With this type of arrangement it is just not possible to get a grip in the small size of the bolt at or below the nut.
You will be far better off using a mini hand hacksaw as shown in another answer or a Dremel tool with a grinding wheel cutoff blade.
An alternative if you do not have a Dremel tool but do have an oscillating tool is to use a metal cutting blade in that. Note that it is my experience that the typical metal cutting blades for these saws do not last as long as you would hope and they are much more expensive than a few cutoff wheels for a Dremel tool.
Cutting the bolts might not be the best solution. Closet bolts are typically made of brass which does not rust. However, there can certainly be other types of corrosion present, as well as dirt, grime, and mineral deposits if water got in there (you do need to replace the wax ring, after all). This means that the nuts are likely not fused to the bolts, but just need some encouragement to break loose.
Before attempting to remove the bolts, I recommend spraying them with a product such as Penetrating Blaster.
Let it soak into the area around the nut for a minute or two. Next, get a socket wrench and pick the smallest socket that will fit over the nut and torque it free. If you cannot get the nut to move, try using a breaker bar which provides more leverage. If you do not have access to a breaker bar (you really should have one and they do not cost a lot), you can improvise with a box wrench and a narrow metal pipe slipped over the handle (cheater bar).
Cutting those bolts would be further down on my list of options. In order to keep the toilet firm on the floor without rocking back and forth the bolts should be moderately tight. Cutting through one of them may cause a sudden shift of weight which may cause damage such as cracking the porcelain near one of the bolt holes, or the saw blade may nick the enamel coating on the toilet. If you must use a saw, I would prefer a rotary tool such as a Dremel with the proper metal-cutting blade. Be sure to wear both gloves and safety glasses, move anything flammable away from the work area, and cover trim, drywall, anything nailed down that you do not want damaged. This will create a lot of hot sparks.
Toilets are fragile. This is a recipe for cracking the toilet (then finding out the tank and base are unusual and effectively a matched set, and now you need a whole new toilet and how do you dispose of an old toilet in this city?)
You want low-violence, low-impact methods.
Both of them apply little enough force that they are unlikely to crack the toilet when they slip. However they will take awhile.
Typically closet bolts are brass so I'm a little surprised to read that they are rusted. One option that I don't think has been mentioned is that if you can just use a socket wrench to snap the nuts/bolts off.
Take a socket wrench with an extension so that the handle is a few inches above the base sticking forward from the toilet. Take a length of pipe a foot-and-a-half or so and place if over the handle. This extra leverage should allow you to 'persuade' the nut to move, or if it's really on there, the bolt will snap. Either way it should come off. It might be tricky in a really tight bathroom but something to consider.
My usual course of action involves using a Dremel with a cutoff wheel as @ Michael Karas has suggested. My technique involves cutting off and bolt that extends through the nut. Then cut vertically through the nut. By moving slightly from left you will cut the nut and not hit the porcelain. A thin piece of cardboard with a small hole placed over the nut may provide a little extra protection if the tool slips.
When I added new bolts to the toilets I replaced, the bolts came longer than they needed to be (helps with installation) but there's a bare spot for cutting to proper length. I used my angle grinder with a 1mm cutting disc to cut them off.
I would caution against using any kind of motorized movement tool as well (the aforementioned oscillating blade or a reciprocating saw) because the same dangers of cracking the toilet apply. A grinder or Dremel will apply steady directional pressure. Anything that moved the blade back and forth (especially on metal) may have unpredictable movements if the blade binds up.
Um, the real problem is stuck bolts. Perhaps you should try heating the bolts up with a blow torch. This works beautifully for anything where you can apply an open flame without damaging the surrounding area. If you are worried about damage you can surround the work area with a welding blanket or even a sopping wet towel that you don't care about destroying. Heat those suckers up and then immediately put a wrench on them and start turning. If you can get the nut to move a little bit, spray some PB Blaster or Liquid wrench on there, tap it lightly with a hammer (repeat a few times) and then remove the nut with a wrench.
My primary socket set is a fantastic Craftsman set with hollow centers. No matter how long the bolt the socket wrench slides right on. Something like that would work perfectly for this situation. I'd recommend that tool set, but you can probably get a deep socket on there as well which would be a big help.
Also, it would probably behoove you to take a wire brush and clean up the exposed threads as best you can before removal.
My Dad swears by Liquid Wrench and he is an absolute master at removing stuck/rusted bolts. He would say spray the crap out of it with Liquid Wrench, tap it and repeat. The tapping is to vibrate the bolt/nut so the Liquid Wrench can work into the rusted nut. Let it soak in Liquid Wrench for as long as you can. (Whenever I'm planning on disassembling a rusted part I try to Liquid Wrench/PB Blaster it for DAYS leading up to the actual "work")
When you go to put everything back together, obviously use stainless steel or brass hardware if it's new, but also definitely coat the bolt threads with some Anti-seize
Instead of attacking the problem from below the toilet bowl, you could work from the top. The bolt will have a flat top that you can see on the bottom of the flush tank. You can use a dremel to cut it off, but a simpler option would be to drill in the center of the bolt head with a drill bit larger than the bolt diameter. Once you drill through, the head will split from the bolt. I've done that before in the same situation. It works quite well.
Next time make sure the bolt is stainless...
-- A bit of clarification... our toilet tanks here (France) are mounted with this kind of stuff:
The bolt head and rubber cone go into the tank, and the rest pokes out of the bottom, which results in something like that:
So the method I used was to drill the head of the bolt off. It works pretty well.
