Sunday, January 29, 2023


Make your toilet “rise” to the occasion — Install a riser!

Don’t know if it’s age, or if earth’s gravity is somehow getting stronger. As an example, whenever we’re called on to do work at floor level, our bones groan with the thought of having to get back up. Answer: Just avoid floor level work! But that doesn’t help “when nature calls.” Sometimes getting up from that toilet seat is a groaner on the throner! There’s a way to make trips to the terlit easier. Make your toilet rise to the occasion by installing an RV toilet riser.

Tips and tools

Thetford, maker of many RV toilets, also produces an RV toilet riser. The device gives RV toilets a lift of two-and-a-half inches. Happily, it works not only on Thetford models, but also on toilets produced by other manufacturers, including SeaLand (Dometic). The riser installs on the bathroom floor where your current toilet sits, and the toilet is then mounted atop the riser.

First, take our advice: Dump your black water tank before starting out on this upgrade. You’ll be installing a new toilet flange seal, and shoving your nose down to the vicinity of a full black water tank ain’t the best thing for your senses.

The right tools make it easier to remove the toilet. Some simply need an end wrench; others are a bit more complicated, requiring a ratchet and socket, plus an extension, and possibly a universal joint. If you are mounting a SeaLand toilet, you may want to buy a single new closet seal as it is a bit larger than those used on Thetford toilets. If yours is a Thetford, you’ll find the seals you need in the riser package.

Check out your toilet’s water supply line. With the extra lift the riser gives to your toilet, you may need to extend (or replace) the water supply line to account for the extra height. In our case, we decided to ditch the old solid plastic water lines and install a new flexible toilet supply line, with the addition of a shutoff valve. In the end we really blessed ourselves for that decision.

IT’S NOT A BAD IDEA to have some cleaning rags and spray cleaner on hand. Once you pull the toilet off the floor, you may find an accumulation of dirt and grime just itching to be sent away.

Upside-down that toilet


Shut off the water supply to the toilet and drain the toilet bowl. You’ll then turn the toilet upside down for the installation, so getting the water out is a must. Disconnect the toilet from the existing toilet mounting bolts that hold it to the floor.

Likely the old toilet flange seal will be hanging onto the toilet for dear life. Too bad! Pull and toss away the old seal and clean up the bottom of the toilet. You’ll also remove the old toilet hold-down bolts; they are useless for the new installation. Clean up the bottom of the toilet and install the new flange seal.

Depending on where your water supply line comes in, you may need to modify the toilet riser. If the supply line comes up through the floor, the new riser may cover it. In that case you’ll need to drill a hole in the riser to accommodate the plumbing line. Thetford’s instructions will provide you with possible locations for the hole.

In our case, the water line didn’t come up through the floor, but from the wall immediately behind the toilet — and in an area impacted by the riser. Rather than trying to cut a hole through the side of the riser, we relocated the line. More complications! The water line was in a “dead space” in a cabinet behind the toilet. This added a considerable amount of time to the installation, but we were happy with the results.

Finicky flange?

riser-on-floorAs mentioned, the new riser fits on the floor — and you’ll find new flange bolts which pass completely through the riser, then into the toilet. Instructions in the kit advise which of the two sets of bolts you’ll use. You’ll also find two flange seals. Again, if you’re installing a SeaLand toilet, you’ll use your own new SeaLand seal; otherwise put one of the new flange seals from the kit on the bottom of your toilet flange. This gasket forms a new seal between the base of the toilet and the top of the riser. You’ll also install a new seal gasket over the flange on the bottom of the riser. Here you’ll use one of the seals from the riser kit.

Pick the right flange bolts and position them in the floor flange. Next, line up the riser so the word “front” will be where the front of the toilet will be located. Now simply lower the riser down over the bolts. This is where it gets tricky. Those hold-down bolts probably won’t stand real still, and you’ll be basically threading the bolts through little holes in the riser. Since most RV bathrooms are pretty tiny, you won’t likely have room for a helper to assist you in the alignment process. For some, liberal applications of the appropriate refreshing beverage may be called for.

Bolt trick

Once you have the riser settled down on the floor flange, line up the toilet and drop it down over the hold-down bolts. This is a bit easier since the bolts will be less inclined to wobble, now that they’ve been “collared” by the riser. However, you’ll be fighting against the collective efforts of two springy rubber flange seals. Here’s where a helper may be helpful. Have the helper sit on the toilet so his or her weight will compress the flange seals enough to get the bolts to come into reach. Quickly get hold-down nuts tied onto the threads and start running the nuts home. With your helper off the pot, tighten the nuts until all rocking motion is taken out of the installation. If your bathroom floor is carpeted, it may take considerable doing.

Some RVers who’ve wrestled with lining up the flange bolts to get them where they belong have found a “bolt trick” to help. With the flange bolts in place, they put plastic drinking straws over the bolts, then use those sippers as a guide for lowering the toilet into place. Once in place, yank out the straws and proceed with the nuts.

Will it be steady?

The riser raises the toilet by two-and-a-half inches. We’ve heard other RVers swear off the idea of installing one because they worried the toilet wouldn’t be steady. Hang on, it’s a matter of snugging those nuts on the flange bolts down good and tight. But that can present an issue of its own.

In our case, we fought like mad to get the toilet pushed down far enough to get the top of the hold-down bolts to come through the base of the toilet. At first blush it looked as though we needed the longer hold-down bolts, so we pulled the riser, replaced the bolts with the longer set, and went through the frustrating part of lining everything up. This time the bolts came into easy reach, but alas! When we tightened down the toilet, the bolts were indeed too long, and we couldn’t tighten the nuts down far enough without the tops of the bolts impacting the toilet itself.

That meant tearing everything out again, putting in the correct bolts, and by carefully “mooshing” the toilet down to overcome the resilience of the flange gaskets, we actually got some bolt threads in reach of the mooring nuts. When they tell you which bolts to use, believe what you read.

Where to find them

If you want to proceed on this as a project, be sure to shop around. Prices for Thetford risers vary widely. On the Internet you’ll find prices (including shipping) range anywhere from a low of $30 to the mid-$50 range. [Editor: Here are some at Amazon for comparison.]

While this riser will fit all Thetford toilets and most SeaLand models, it will NOT work with SeaLand’s 511 and 911 models; nor will it function if your SeaLand uses a SeaLand “universal mounting unit.”

Was it worth the effort? Absolutely! Easing down to sit is much easier, and when it’s time for “liftoff,” getting a two-inch jump on gravity can make a huge difference on those knees and other recalcitrant body parts.

Got a mod or upgrade of your own? We’d love to hear about it. Drop a line to Russ (at) .





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14 days ago

We have the Thetford riser with a Dometic 310. Unfortunately there’s a very slow leak of urine at the base wher the toilet is seated on the riser. Being plumbing challenged we are having it either repaired or replaced but without the riser.

Jim Johnson
14 days ago

You didn’t mention the ‘why’ of putting in a shut-off valve on your toilet supply line. I’ll add mine. The RV toilet valve is typically the weakest, most likely to fail valve in your fresh water system. Without a shut-off, when (rarely ‘if’ in my opinion) the toilet valve goes you lose use of your entire water system. With a shut-off you can use the rest of your water system and still ‘flush’ your RV toilet with a bucket or jug of water. A shut-off has been a real vacation saver twice in our experience.

14 days ago

When we built our new home after Hurricane Harvey, we installed ADA compliant toilets. You will not want to sit on any other toilet again.

Tommy Molnar
14 days ago
Reply to  TexasScout

So true! We’ve installed ADA toilets in our house and now wonder how we survived without them!

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