Is it possible to replace the boiler's hot water tube without emptying the tank?

Question

After 3 years living here, the flexible tube in the output of the boiler burst. That is when I noticed that the hot water tube (blue and red stripes) was installed in the cold input, and the cold water tube (just blue stripes) was installed in the hot output (see attached image).

The hot water stopped spraying after I closed the water supply.

How do I replace hot water tube without dumping 100 l of (dangerously hot) water on the floor?

If I keep the water input closed, will it leak when I remove the broken tube?

Should I drain the tank first? If so, how? And how do I fill it up again afterwards?

EDIT: added full body picture

Answer 1

You actually don't need to drain the tank much.

Not sure if the other answerers are familiar with the design of European-style hot water cylinders like this one, but it's basically like this:

• Cold water inlet goes right to the very bottom of the tank
• Hot water outlet is connected to a vertical riser pipe inside the tank, going all the way to the top

Hot water is less dense and rises up, which is why it has to be collected from the top. This approach ensures that as you consume hot water in the tank, cold water is refilled from the bottom (where the heating element is) and does not mix with the hot water at the top. The temperature of the hot water thus stays constant until the tank is used up completely.

A consequence of this design is that as soon as you drain a little bit of water from the tank, the water level will drop below the top end of the riser pipe and the hot water outlet will go dry.

This draining might have already happened, but it is very possible it hasn't. Get a bucket (or two), hold it under the hot water outlet, and carefully loosen the flex hose. Most likely, water will start coming out unevenly with a glug-glug-glug (there's no other way for air to enter the tank, so air bubbles will have to take turns with water in the hot riser pipe). After perhaps 10 litres, it should be done draining and you can then safely replace the hose.

You can help it drain by operating the red lever on the pressure relief valve after undoing the hot water hose (so that water can come out the bottom port and the hot water riser will be for air only).

Answer 2

Emptying

1. The plastic tube coming from the red handle circled in green is the drain. Investigate where that goes. It hopefully goes outside or into a drain. Make sure!.
2. Close the cold supply valve (in the red circle), leave the hot water valve open and open the highest hot water faucet in the house, or at least one that is higher than the top of this tank. This will admit air while the tank drains.
3. Open the red drain valve circled in green. The tank should now drain through the clear plastic tube in the picture.
4. Check again at the other end of the clear tube that the water is draining to where you want it to drain, that the tube isn't cracked or leaking and the water is not collecting anywhere.
5. When the water stops draining disconnect the two hoses from the valves in the red circle. Expect a little water out of them so have a bucket ready.

Refilling

After reconnecting all the hoses:

1. Close the drain valve, open both of the other valves.
2. Turn on any hot water faucet and wait for cold water to come out then close the faucet. This fills the tank with cold water.
3. Power up the boiler and wait for it to heat up.
4. Test from a few faucets. Expect air out of every faucet the first time you use it.

Note

You must connect the cold supply to the correct connection on the tank. These must not be reversed. It probably doesn't matter if the hoses are reversed, IE you use the wrong color hose for hot and cold, as long as the tank is connected the right way around. The hoses are probably identical and colored differently just to help you get it right.

Answer 3

Based on this statement:

the flexible tube in the output of the boiler burst. ... The hot water stopped spraying after I closed the water supply.

I suspect the pressure inside the tank has run down through the crack in the hot water flex pipe. I believe it may be possible to replace the flex pipe without draining the tank (if the tank hasn't drained itself already).

Water heaters are sealed units, so if the cold water is kept off, the water should tend to stay inside the tank, similar to how one can lift a straw-full of liquid out of a cup by plugging the top of the straw.

I would also suggest a suitable quarter-turn valve (if your local code allows it) on the hot water side, just like the cold water side, so this sort of repair will be easier next time. Then you could merely turn the hot and or cold valves off on both ends of the flex pipes, then replace the flex pipes easily.

Stand by with a bucket capable of holding the contents of the water heater, in case the water is not held inside. Even if it is held inside, a small steady drip could happen.

If you can use another valve, remove the flex pipe, then attach the valve according to instructions, with suitable sealant if instructed. Have the valve open while attaching it, so the leaking water (if any) flows through the valve and doesn't get in the way too much while threading the valve on. Once the valve is on, close it, then attach the new flex pipe at your convenience.

If you cannot use the extra valve, replace the flex pipe according to instructions.

Filling afterwards: Remove aerators from the house faucets, so dislodged gunk in the pipes doesn't block the faucets. Turn on all valves at the heater, and and a hot water faucet (perhaps all the hot water faucets in the house). Let the water run, and let air bubbles clear through the plumbing. Once no air bubbles appear, start the heating system in the heater.

Answer 4

OP has stated the picture is showing the correct placement of the tank. Making this answer useless for this question.

Seeing it stopped leaking guessing the picture is upside down.

Should be a drain near the bottom of the tank.

Might not need to drain any, but usually good to drain some(couple litres/half gallon) every couple of months to remove sediment.

With power and shut off valves off, replacement/moving of the tubes should be easy. Drain a bit to remove pressure or leave a hot faucet open.

Answer 5

Based on the design (input on the bottom) you will need to drain the tank.

You can simply (after shutting off the power) turn off the input and turn on the drain. Once it's drained and you do your work, turn on the water again, and restore power once it has water flowing.

Answer 6

There is no way around it you must drain the boiler.

The water is under pressure in the boiler at least 30 or more psi.

Close the cold water supply and open hot water faucet in your home.

You also have a drain hose with valve that you should open to assist draining.

The drain hose goes somewhere true the wall, hopefully to the outside,

Answer 7

You can probably get away without draining the tank much if you work fast and only have one connection open at at time.

Disconnect one hose cap that outlet, the cap will prevent siphoning wwhen you disconnect the other outlet. disconnect the other outlet reconnect that outlet. uncap and reconnect the other.

You will be working with hot water so, wear thick rubber gloves and have plenty of cold water on hand in-case you burn yourself.