A showroom provides you with two shapes. One has a visible seam where the tank bolts down onto the bowl. The other is a single moulded body with no joint at all. The difference in price is literally hundreds of dollars. Most buying guides end at looks, cleaning and cost. Those matter, but they forget to include what a plumber cares about. This guide explains the true difference between the two designs; the Ontario regulations they both need to comply with; what parts do not work on each one; and how the decision applies to an older home in the GTA. The Difference, in One Line A two-piece toilet consists of a bowl and a tank. The two get bolted together on site, with a rubber gasket sealing the joint. A one-piece toilet is manufactured as a single piece. The tank and bowl are fused, and there is no joint to seal. This is the only structural difference between the two types. Almost all other claims you see regarding the two designs can be traced back to it or a feature that has nothing to do with it. A Skirted Base Is a Separate Choice Buying guides hand one-piece toilets the credit for a smooth, hidden trapway. The two have no correlation whatsoever. The trapway refers to the S-shaped channel that removes waste from the toilet bowl. In a typical toilet bowl, the exterior surface of the china will also feature these bends. Skirted models will hide them behind a flat panel making the toilet appear as one column from top to bottom. All of TOTO, Kohler, Duravit, American Standard and Caroma offer their skirted counterparts to their flush platforms available in the conventional trim. One example of such a model is the Glacier Bay Caspian toilet available at Home Depot Canada, a two-piece model with a concealed trapway and skirted design. Skirting is bodywork, not plumbing. The flushing engine underneath does not change. You can find a skirted two-piece toilet; you can also get a one-piece toilet with an exposed trapway. The problem is the service access. The skirt conceals the places through which the closet bolts usually pass through the base, so a skirted model must be secured to a mounting bracket that has been mounted to the floor first. Detaching one for service becomes an extra procedure, and shimming the uneven floor becomes tricky. Once the floor is out of level by about a quarter inch across the footprint, shimming will be necessary. Cleaning: What the Seam Actually Costs You A two-piece has more joints than a one-piece, and dirt accumulates in the places that are difficult to reach. Bolt covers stand on either side of the base. There is a space between the tank and the back of the bowl. You clean around all of it. A one-piece eliminates the gap and the caps. This saving is genuine, but small. Think a couple of minutes a week. There are two things more important than the seam. A skirted base eliminates far more cleaning surfaces than the fused tank does. Neither of these designs helps to clean the gap behind a tank mounted to the wall. Flush Power Has Nothing to Do With the Shape Neither design flushes better than the other. Flush efficiency is model-specific, and there is a rating available to the public. A MaP test determines the amount of solid waste that can be flushed away during one flush in a particular toilet using soybean paste and toilet paper as test media. The maximum capacity of the scale is 1,000 grams. The WaterSense standard is 350 grams, and MaP classifies everything above 500 grams as outstanding. Average scores of tank-type toilets have increased from 336 grams in 2003 to 882 grams by March 2017. Check your model in the MaP database prior to buying. This number is model-specific, not shape-specific or price-specific. The Ontario Rules Both Designs Have to Meet According to the Ontario Building Code, every toilet installed in this province has to comply with CAN/CSA-B45.0. For a house, it limits the flush volume to 4.8 litres. Dual-flush models are considered compliant if they provide both 4.1 litres/less and 6.0 litres options. The most common “gallon” conversions found on most labels sold here are based on 4.8 litres (1.28 US gallons). Both designs are built to it, and neither of them is exempt from it. Older buildings can get relief where a building official accepts that compliance is impractical. This is a small allowance. It does not apply to a typical bathroom exchange. Repairs: The Parts That Actually Fail Fill valve, flush valve, and flapper wear out on every toilet. A running toilet usually means failure of one of the two valves. Both valves are inside the tank in both designs, cost a few dollars each, and installation takes less than an hour. No advantage either way. The difference is evident in two places. The two-piece design introduces additional joints. A leak at the tank bolts or the flush valve requires the tank to be removed from the bowl to replace the bolts, washers and gaskets. Those components are stored on the shelf at every supplier. The usual problem with this joint is caused by overtightening the tank bolts during a DIY installation, which can cause the china to crack. The one-piece removes the joint and raises the stakes on the body. In the case of cracks in the tank on a one-piece, there is only one effective solution and it is replacement of the whole toilet. In the case of a two-piece, you purchase a replacement tank and keep the bowl if the model is still in production; parts availability should be checked prior to purchase of either shape. There is a second risk for older one-piece models. Some have non-standard internals which are not going to be compatible with the universal kit. Our toilet repair and installation team sources parts for out-of-production models throughout the GTA. Installing One in a Real GTA Home A one-piece usually weighs between 88 to 120 pounds and will have to be moved in one single lift. On the other hand, a two-piece toilet separates into a bowl which weighs 50 to 60 pounds and a tank weighing 25 to 40 pounds. That gap decides things in a second-floor bathroom off a narrow hallway, or a condo unit reached by one service elevator. Rough-in comes next, and it beats every other measurement. Rough-in is the distance from the finished wall to the centre of the closet bolts. The standard is 12 inches, with 10-inch and 14-inch versions made for older homes. Measure from the wall, not the baseboard. A one-piece does nothing to solve a rough-in mismatch. The drain location in your floor sets that number, not the toilet’s construction. A two-piece gives you a little more room to work with, as the bowl stays the same and you order a different tank. Then there is what sits under the old toilet. Toronto’s older housing stock hides corroded flanges, soft subfloor around the closet bend and shutoff valves that seize the first time anyone turns them. A sound flange is a simple reset. A corroded, cracked or recessed one adds repair work before the new toilet can sit. Any of that turns a one-hour swap into a half-day job, whichever shape you picked. Your Drain Matters More Than Your Toilet Every guide on this topic stops at the fixture. A 4.8 litre flush carries less water into the sewer lateral than the 13 and 20 litre toilets it replaces. In a house with a sound lateral and proper slope, that is fine. Toronto and the older inner suburbs are full of vitrified clay laterals with root intrusion and settled joints. Drop a low-flow toilet onto one of those, and the new fixture takes the blame for backups the drain was already heading toward. If your current toilet needs plunging often, or the basement floor drain gurgles during a flush, the problem sits past the fixture. A sewer line video inspection puts a camera inside the lateral and settles the question before you spend money on china. Root damage caught early stays a spot repair. Left alone, the joint keeps opening and the fix becomes a full sewer line replacement under the front lawn. Which One to Pick Choose a two-piece if: Your bathroom has a 10-inch or 14-inch rough-in The bathroom sits upstairs, down a narrow hall, or in a condo with tight access You want the widest choice of heights, bowl shapes and price points You would rather replace a tank than a whole fixture years from now Choose a one-piece if: Cleaning time around the base bothers you The bathroom is small and a compact footprint helps You want a modern look and the budget covers it One less joint in the fixture appeals to you Do this either way: Measure the rough-in before you shop Check the model’s MaP score Confirm 4.8 litres per flush, or a compliant dual flush Treat the skirted base as a separate decision Table Of Contents Frequently Asked Questions 1. Is a one-piece toilet worth the extra money? It buys easier cleaning and one fewer joint. It does not buy a better flush. On a tight budget, put the money toward a higher MaP score instead. 2. Do one-piece toilets leak less? They remove the tank-to-bowl gasket, which is one common leak point. The other is the wax seal at the floor, and both designs share that one. 3. Can I install either one myself? A two-piece is the more manageable DIY job. A one-piece needs two people. Both need a working shutoff valve and a sound flange, and a skirted base adds a bracket step. 4. Which design lasts longer? The china outlives its internals on both. Seals and valves are what wear out. 5. Are one-piece toilets always skirted? No. Skirting is a separate feature, and manufacturers sell it on both designs. 6. What flush volume can I buy for a home in Ontario? 4.8 litres per flush, or a dual-flush unit offering 4.1 litres or less along with 6.0 litres.
