How to Install a Bidet: What You Can DIY and When to Call a Plumber

What kind of bidet are you actually installing?

Three different products get called a bidet, and they are three different jobs.

• A bidet attachment is a thin plate with a nozzle that sandwiches between the toilet bowl and your existing seat. Cold water only on most of them, and no electricity.
• A bidet seat replaces the seat. Non-electric versions run straight off the toilet supply. Electric versions add a heated seat, warm water and a dryer, and they have to be plugged in.
• A standalone bidet is a separate porcelain fixture beside the toilet, with its own faucet, its own trap and its own drain.

The first two are homeowner work. The third is a remodel.

How to install a bidet seat, step by step

Everything on the supply side happens at the angle stop under the tank and the fill valve on the bottom left of the tank. You need an adjustable wrench and a towel.

1. Close the angle stop, then flush and hold the handle down to drain what is left in the tank.
2. Disconnect the flexible supply line where it meets the bottom of the fill valve. Water comes out. That is what the towel is for.
3. Thread the T-connector from the box onto the fill valve inlet with its cone washer seated. If the T is plastic, hand tight only. Plastic T-connectors crack when somebody puts a wrench on them.
4. Reconnect the original supply line to the bottom of the T.
5. Run the bidet's own hose from the side port of the T to the inlet on the seat.
6. Pull the old seat bolts, set the mounting plate, slide the new seat on until it clicks.
7. Open the angle stop slowly, a quarter turn at a time, and watch all three joints.

Before you walk away, wipe every connection dry and lay a fresh square of toilet paper under each one. Check it in an hour. Paper will show you a weep that your eyes miss.

Does a bidet need an electrical outlet?

An electric seat does, and there is no way around it. TOTO's installation sheet for the Washlet E200 calls for grounded 120V, 60Hz current, rates the unit at 410 W, and states that the power cord is 3 feet (1m) long. It also says not to install the unit in a wet or damp place such as a shower stall or tub area (TOTO Washlet E200 installation instructions).

Three feet is the detail that catches people out. The receptacle has to sit behind or beside the toilet, grounded, on a GFCI protected bathroom circuit. An extension cord is not a substitute and the manufacturers say so. If your half bath has no receptacle at all, which happens plenty in the older houses around Sonoma and Marin, you are adding a circuit before you are adding a bidet.

Non-electric seats and attachments skip all of that. Line pressure does the work.

Where does the warm water come from?

Electric seats heat it on board. Non-electric warm water seats do not. They have a second inlet that tees into the hot side of the sink, usually at that fixture's angle stop, with a line run over to the toilet. Where the sink sits right next to the toilet, that run hides inside the vanity. Where the sink is across the room, it means opening a wall.

Check your pressure too. TOTO specifies a supply of 20 to 80 PSI for that same seat. Under 20 and the spray is limp. Over 80 and you are chewing up every fixture in the house, not only the new one, which is a problem worth fixing on its own.

What does the plumbing code expect from a bidet?

The water supply to a bidet counts as a high hazard cross connection, because the nozzle sits in the airspace of a toilet bowl. Code wants it protected by an air gap or a backflow preventer. Listed bidet seats and attachments handle that inside the unit and carry the ASME A112.4.2 / CSA B45.16 certification for personal hygiene devices. So buy a listed unit and skip anything improvised out of a hose splitter and a sprayer.

A standalone fixture is a different animal. Kohler's roughing-in sheet for the Memoirs vertical spray bidet calls for a 3/8 inch cold stop and a 3/8 inch hot stop, a 1-3/4 inch drain hole in the fixture and a 1-1/4 inch OD drain outlet (Kohler K-4886 roughing-in sheet). Hot and cold rough-ins in the wall or floor, a trap, a vent, and in most of Sonoma County a permit.

When should you call a plumber instead?

• The angle stop will not close, or it weeps once you reopen it. A lot of houses here still have the original multi-turn stops, and a valve nobody has touched in twenty years does not always seal again. Swapping it is a small job. Learning that on a Sunday with the water on is not.
• There is no outlet and you want the electric seat. That is an electrician's circuit, then the fixture work.
• You want a standalone bidet. Supplies, drain, trap, vent, permit.
• Your toilet is one-piece or French curve. Plenty of bidet seats will not sit flat on those. Read the seat maker's fit list before you buy, not after.
• You want warm water without electricity. Teeing a hot line over to the toilet is real plumbing.

We do fixture swaps and new fixture installs for remodels all over Sonoma and Marin, and quotes for that work are free, so you get a number before anyone opens a wall. Faucet and fixture repair is one of our everyday calls. Phone is (707) 308-5599.

Are bidets worth it?

For a non-electric seat or attachment the bar is low enough that the question mostly answers itself. The hardware is cheap, the install takes one wrench, and nothing about it is permanent. Pull it off, put the old seat back, and the bathroom looks like it always did.

Electric seats are the real decision. You are buying a 410 W appliance that lives in a wet room and wants its own grounded outlet. People who have one tend to keep it. The outlet is the hidden cost, and it is cheaper to price that first than to find out after the box is open.