DIY Network

How to Install an Instant Hot Water Tank

Use these instructions to install a system under the sink that provides hot water without the wait. Some high-end models even come with a water filter system and cold water dispenser.

More in Plumbing

Step 1: Shut Off the Water and Power

Clean out the area under the sink to make room for the tank.

Next, shut off the water at the water heater.

Turn off the power at the breaker. If your water heater is gas, turn the control to the 'Pilot' setting.

shut off water at water heater

Step 2: Drain the Lines

Drain the water lines. Turn on the faucet at the sink where you are working, as well as an outside faucet.

Note: If there isn't an existing hole in the sink, a hole will need to be cut for the water dispenser.

drain the water lines

Step 3: Mark the Sink

Make a dimple into the sink where the dispenser will be placed, using a drill set and hammer.

mark sink with dimple where dispenser will be

Step 4: Drill a Hole, and Smooth the Edges

Using acordless drill and a stainless steel bit, drill a 3/4" hole into the sink (Image 1).

A slug buster can also be used to cut the hole. To do so, take the cutting wheal off the slug buster (Image 2). Place the slug buster into the hole, then reattach the cutting wheel underneath. Hand tighten the nut on the top side of the slug buster, then use a wrench to continue tightening until you hear a 'pop' (Image 3). Remove the slug buster.

Use an emery cloth to smooth the edges

Safety Note: Always wear safety glasses when cutting metal.

Note: If the sink is cast iron, make the cut into the countertop near the sink using a hole-saw (Image 4).

Step 5: Place the Dispenser Into the Sink

Place the seal ring to the underside of the dispenser (Image 1).

Place the dispenser into the sink.

Attach the mounting ring from the underside of the dispenser over the threaded rod (Image 2).

Add the hex nut, then tighten to secure.

Step 6: Connect the Water lines

Loosen the compression nut at the cold water stop under the sink, then remove the line.

Install a double compression stop to the water line, then reattach the lines to the sink.

install double compression stop to water line

Step 7: Mark a Spot for the Tank

Position the tank close to the plumbing and the electrical outlet. While holding the tank in place, draw a line on the wall to mark the top of the tank.

mark top of the tank

Step 8: Hang the Tank, and Connect the System

Attach the mounting bracket 1" from the line using a drill bit and 1" wood screws. Hang the tank on the bracket.

Push the blue tubing into the quick-connect fitting on the tank. Slip the clear vinyl tube over the fitting in the middle. Connect the larger tube over the last barbed fitting.

hand tank and connect the system

Step 9: Mount the Filter, and Add Lines

Attach the mounting bracket near the tank, then attach the filter.

Connect the 3/8" tubing from the outlet side of the filter to the 3/8" Y fitting.
Add the clear vent line to the filter (Image 1).

Insert both copper lines from the dispenser to the Y fitting (Image 2).

Step 10: Attach the Double Compression Stop

Attach a compression nut over the 3/8" tubing. Then, attach to the double compression stop installed at the existing water line and tighten.

insert copper lines

Step 11: Turn on the Water and Finish Installation

Turn the water back on at the water heater.

Open the water stops under the sink, then check for leaks.

Open the cold water faucet at the new dispenser to wash out the filter. Turn off the cold water faucet, then open the hot water faucet until water begins to flow.

Plug in the tank.

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