Installing a Japanese Toilet Seat




This guide is to install a japanese-style toilet seat in a US house.

I believe the plumbing is safe, but it has not been checked to code. I am not a plumber and some plumbers may not approve of this method. I am also not an electrician- The wiring I used technically falls under "Temporary wiring" and doesn't fall under most electrical codes that I know of. Wiring should be on a GFCI outlet and include a drip loop. I am not responsible for any damages, mishaps, floodings, etc that may occur by following (or not following) this guide.

You will need-

1. A Japanese toilet seat with a 1/2" FIP connection. This seems to be the standard connection for Japanese toilets seats even though Japan is a metric country. I am using the Toshiba SCS-T160 (new model seems to be SCS-T175?), which has worked fine for 2 years on US 120V power. This toilet seat is not intended for export from Japan. The "Export" marketed toilet seats are much more expensive and probably have different connections.

1.a. All the accessories that came with the Japanese toilet seat

2. medium to large size adjustable wrenches, you will need 2 (TWO)

3. A Sioux Chief Mfg 660-TK Female Swivel Ballcock Nut by Male Ballcock Thread Mini Rester. I couldn't find a local store which carries this so I got mine on Amazon.

4. Flathead screwdrivers, 1 medium/large one is probably required, 1 very small one might be helpful

5. Teflon pipe tape, available from any hardware store

6. 1 3/8" flare to 1/2" Male Iron Pipe (MIP) adapter. I used the Watts A-184, which can be found at Home Depot or Lowes.

7. Towel or paper towels to wipe up water (not your best guest towel)

8. (Possibly required) 1 Toilet connector hose, 3/8" Compression by 7/8" Ballcock threads. This is needed if your existing plumbing is pipe rather than hose. Pay attention when buying this because faucet connector hoses look almost the same but are different sizes from what is required here.

If you are unfamiliar with plumbing threads, we have several different types of threads in this project. 3/8" compression, 3/8" flare, 1/2" male/female iron pipe [MIP/FIP], and 7/8" ballcock. All of these threads are incompatible with each other. The 3/8" compression is a slightly different size than the 3/8" flare, which is a slightly different size from 3/8" FIP/MIP. 7/8" ballcock is a special thread size which is only used on the bottom of a toilet tank and nowhere else, so it is incompatible with everything.


Step 1: Remove the Old Seat and Turn Off Water

Remove the top of the toilet tank.

Remove the old toilet seat, this probably requires a flathead screwdriver.  Set it aside and keep the hardware with it (for when you move out).

Now would be a good time to make sure you know where your whole-house water shutoff is.  Mine was in the basement.  If you make a big mistake you should close this valve.  Yours may or may not have a broom next to it.

Next, close the local shutoff valve next to the toilet.  Flush the toilet and hold down the lever until the tank is basically empty.  If the water is coming into the toilet, close the shutoff valve some more.

Step 2: Remove Old Piping

If your toilet has solid metal piping from the valve to the toilet tank, follow [S].
If your toilet has flexible plastic tubing or flexible braided metal tubing already,  follow [F]

Remove the metal tubing from the valve to the toilet tank using an adjustable wrench.  Install a flexible toilet connector tube- in most cases in the US this will be a 3/8" compression fitting to a 7/8" ballcock fitting.  You can throw the solid metal tubing away later, but for now just set it aside.  Refer photos 1 to 4.

Remove the 7/8" ballcock fitting from the toilet tank.  Leave the connection to the valve alone.  Refer photo 4 only.

Step 3: Prepare Ballcock Tee and Install

Next, grab your Sioux Chief 660-TK mini-rester.  It would be great if they made a male ballcock to Female ballcock Tee connector that you could use for this project, but they don't.  I tried contacting Sioux Chief about this but they never got back to me.  So we're going to use the fitting and throw away the "mini-rester".

Now you may ask yourself, "Self, why am I buying this $20 part and then throwing away the most expensive part of it?"  A fair question.  The reality is you could probably make the plumbing connection another way, but other methods have disadvantages too.  The reasons I am doing it this way is because-
1. Other methods which are cheaper require more skill or more tools than this method 
2. This method can be easilly removed later (without tools!)
3. This method is less likely to leak since the number of connections is lower
4. Other methods are actually almost the same cost since there is no 1 "perfect" fitting for this project and several fittings are required.

First, unscrew the mini-rester from the fitting.  You will need 2 wrenches.  Be careful not to damage the threads or the plastic nut.  

The mini-rester should have an O-ring on it.  Remove the O-ring.  A small flathead screwdriver might be helpful.

Put the O-ring onto the 3/8 in. x 1/2 in. Brass Flare x MIP Adapter (Watts A-184 or similar).  Wrap the 3/8 Flare portion of this fitting with teflon tape (not shown). 

Screw the 3/8" flare half of the fitting into the place where the mini-rester used to be.  
This is the portion of the instructable that real plumbers probably won't like.  The Mini-rester has straight threads so a 3/8" iron pipe nipple (3/8" MIP to 3/8" MIP) or 3/8" iron pipe adapter (3/8" MIP to 1/2" MIP) will not work.  "Iron pipe" threads have tapered threads and won't fit.  Only the 3/8" flare fitting will fit.  Note- "Iron pipe" threads can (and often are) made of brass or bronze.  Technically flare fittings should be used with other flare fittings, but in this case we are using the O-ring and the teflon tape to try to make sure it doesn't leak.

We have just made the fitting that we need.  The water supply inlet is 7/8" ballcock male. The water outlet to the toilet tank is 7/8" ballcock female.  The water outlet to the toilet seat is 1/2" male iron pipe [MIP].  Note that Iron Pipe thread is a type of thread, not a requirement that the fitting be made of iron.
Screw the 7/8" male ballcock part of this tee onto your flexible toilet connector hose.  Tighten it hand-tight (do not use a wrench).

Step 4: Install Toilet Seat Hose

The Japanese toilet seat should have a 1/2" FIP to 1/2" FIP (Female iron pipe) hose included in the box.  Connect this to the Tee we made in the last step and to the toilet seat.  Hand-tight should be enough.  Do not use a wrench on the toilet seat connection.

The Japanese toilet seat should also have a mounting bracket included.  The Toshiba SCS-T160 also includes a special wrench to install this mounting bracket.  Install the bracket onto the toilet bowl.  Then install the seat onto the mounting bracket.  Check to make sure that the seat rests where it is supposed to.  Remove the toilet seat and adjust the bracket if necessary.

Step 5: Install Electricals and Finish Up

Turn the water back on and check for leaks. The toilet bowl will fill up.  Do not proceed further (DO NOT plug the toilet seat into power) until leaks are resolved and the water is ON.

Install the electrical connections for the toilet seat now.  Since I am renting, I am using a short extension cord.  If you plan to live in your house a long time, adding an outlet is a better option.  Make sure the outlet is GFCI protected and test the GFCI circuit.  Keep the wires off the floor using zip-ties or wire ties (I used the ones which came with the extension cord).  Make sure you have a "drip loop" - there should be a loop of wire lower than the electrical plug.

(Not shown)
The Toshiba SCS-T160 comes with a 2-prong (ungrounded) plug and a bare wire for ground.  We really should ground this.  I used a Heavy-Duty 3-Wire Replacement Male Electrical Plug just on the ground wire.  Now the toilet seat connects with 2 plugs, one 3-prong (with only ground connected to ground), and the 2-prong (ungrounded) plug.  You could butcher the wire and wire them all up to 1 plug but I was too lazy for that.

Make sure the toilet seat has water supply, and plug it into the electrical supply.  You now have a Japanese toilet seat installed!

If you move, simply shut off the water, flush the toilet (empty the tank), and remove the Tee.  Then connect the flexible supply hose to the toilet tank.  Remove the seat and replace with the old seat.



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      16 Discussions


      Question 6 months ago

      Hello--I am having a heck of time trying to unscrew the mini rester from the fitting. Is there any trick to get it separated? I am using two wrenches. I have even asked several men to try--no luck.

      1 answer

      Answer 6 months ago

      One of mine came off easy, the other one was a bit difficult.

      Longer wrenches might help (I used a 10" and a 12"). If someone has access to a vice, that may help also.

      You could also try some cold/heat. A butane torch would be ideal (I have an Iwatani CB-TC-PRO2) but anything bigger than a cigarette/bbq lighter should work. Be careful not to overheat the bulb part, it may explode.

      If you don't have a torch, or the "it may explode" part scares you, you can try putting the entire part in the freezer for an hour, and then heating up the non-bulb half of it in a pot of boiling water. You will only have a few minutes to try before the temperature equalizes.

      Penetrating oil on the threads might help. My favorite is Aerokroil, but PB blaster and WD-40 are good also.

      Good luck


      2 years ago

      Thank you for this wonderful article. I also have a Japanese Bidet Toilet seat from Toto (TCF-164) that I bought almost 10 years back in Japan but never used it since I was living as tenant over these years. Now since I have my own home, I'm trying to set it up. One problem that I have is with the T adaptor. I had it measured at Lowes which is 1/2" female for water tank, 1/2" male for water supply line & 3/4" male for bidet. My water line has standard 7/8" female connector to the tank. I was thinking of replacing the original T adaptor with a 7/8"X7/8"X3/4" adaptor. I have searched online but so far have found 7/8"X7/8"X1/2" adaptors. I would appreciate it if you could give me some advice on that. I'm posting some pics for your reference.

      1 reply

      2 years ago

      I can't thank you enough for the valuable information to install the Japanese toilet seat so quickly! You are generous to come up with the mini-rester for connecting the existing NA fittings. It took us less than two hours to install the toilet successfully. Yes, we are thoroughly enjoying the Japanese toilet! Thanks again!!!


      2 years ago

      Thank you for your prompt reply to my question. Now I understood why you had suggested the mini-rester. Since our knowledge and skills are far from a plumber, we will take your advice. I will post the results of installation in a couple of weeks.Thanks again!


      2 years ago

      I also brought a Japanese toilet seat back from Japan this summer. We are still doing some research with the installation method & required parts to convert from the Japanese spec to Canadian spec to make this project success. I found your instructions very useful but I have one question. Do you really need a thread mini-rester? What would be the ramifications if I skip this process? Your reply will be much appreciated!

      1 reply

      Reply 2 years ago

      I used the mini-rester only because it was a very convenient way to add a Tee fitting and convert between the pipe threads at the same time. I'm not plumber by trade so it was also safer (less likely to leak) than trying to deal with compression fittings. I threw away the actual water-hammer suppressing device.

      You can hook up the water line using other methods but you will probably need multiple adapters. I don't have any advice on that other than taking the washlet hose to the hardware store and seeing what fits.


      3 years ago

      I had to leave a message to thank you for your work!! I brought a toilet seat back as well and I couldn't figure out any way to connect it until I found your post. Some Amazon and online purchasing and I'm now a proud owner of a working bidet! Thank you so much!!


      3 years ago

      what does those Chinese character means coz i have the same on


      3 years ago

      Just what are the advantages to having this toilet?

      1 reply

      Reply 3 years ago

      The seat I bought is a bolt on seat, not a full toilet.   It attaches to standard size "elongated" bowls.  Does not fit the "round" toilet bowls sometimes used in small 1/2 bathrooms or old houses.

      No-slam lid - Move the lid about 1" away from rest position, and it gently closes by itself without slamming. No need to carefully lower the seat by hand gently onto the bowl. Just flick the lid and it closes itself.

      Water spray, with temperature adjustment and pressure adjustment, "lady" and "butt" spray buttons - my wife couldn't live without it after childbirth. She still appreciates it for "girls days". Great for any occasion when the butt is sensitive (diarrhea, overly spicy food, etc) to clean off irritants before wiping.
      Dry toilet paper doesn't actually clean very well. Spray some water first, just like you would add water to a paper towel when cleaning your kitchen. Then use the paper.

      Self cleaning function for water spray nozzles, cleans before and after each use

      Heated seat - great for cold weather, feels awesome. All the pleasures of a warm seat but without the "ew, someone was just sitting here" thoughts.

      Deodorizing fan with sensor- senses someone sitting on the seat and turns fan on. Sucks air from the toilet bowl through a carbon filter, and exhausts it. Less smelly for next occupant. Also makes a decent amount of white noise to mask bathroom sounds.


      3 years ago

      hey just wanted to say thanks for the
      japanese washlet guide. i went to japan back in november and tossed a
      panasonic washlet in my luggage... got home and had such a hard time
      trying to figure out how to attach it. dedicated plumbing shops had no
      idea. i couldnt get a hydraulic shop to put a new end on the hose. was
      just back to back issues until i found your guide.

      my washlet hose
      was a bit different as it already had a T connector on the end... so i
      basically had to get a plastic end cap for that (metal ones wouldn't
      screw all the way down even though the threads appeared the same)

      thanks again

      2016-01-06 08.18.04.jpg

      4 years ago on Introduction

      I really want to do this one! But, where do you buy this toilet seat, as I'm not going to Japan any time soon...?

      2 replies

      The SCS-T160 is on now sold on Amazon. It is sold in Japan for about $140, with shipping to the USA, $200-230 would be a fair price. The instructions and button labels are all in Japanese but fairly easy to figure out. The most important thing is to only hookup the electricity after the water is hooked up, to avoid damaging the heater.