hot water heater

[amp]

i read a post by "myoldhouse" and it created a few questions.

My current gas hot water heater is 13 years old and I'll need to replace it in the near future. Once I turn-off / disconect the gas, I'll turn off the inlet water to the tank. I have an inlet shutoff for the cold water going into the hot water heater. Shouldn't I have one for the exiting hot as well, so I can cut the exiting hot water heater pipe and not have water drain out? My other question is....If I drain the hot water heater via a garden hose from the tank and shut off the main water going into it (so there's no demand for more water in the tank), will that drain all the water in the hot water lines in the house as well? I'm guessing the hot water lines will drain back into the hot water heater as I'm draining the tank? If I can, I 'd like to put in new shut-off ball valves for my cold and hot lines on the hot water heater.....so when i have to change it again.....i can just cut both copper lines and shut the gas off (and disconnect it) and I'm ready to install the new one. Thoughts on this?????

[CraigFL]

You will be draing the hot water lines back thru the tank drain in the hot water heater. Don't forget to open a few faucets so it will drain quicker.

[sloooo]

Do not add a valve on your hot water side of the heater unless your going to add an expansion tank before the valve. As water gets hot, it expands and if someone closes the valve by mistake, you could burst your tank. You should only have a valve on your cold water line going into the water heater. When you drain your tank, you might get a little siphon of you lines, but that is nothing you should be worried about. When you turn off the cold water inlet to the water heater, crack open a hot water faucet somewhere in the house to release pressure and to make an air vent to drain your hot water heater faster. Install your new heater, check for leaks, and bleed the hot water lines of air and you should be good to go.

[amp]

can i fill up the tank with the garden hose the same way i drained it......................or should i just let the hot water heater ask for water from the main supply and let it fill up slowly?

[househelper]

When the installation is complete, turn on the cold water valve to the tank, open a hot water valve somewhere in the house, and the tank will quickly fill, bleeding out air as it does.

[amp]

i assume as i turn on the supply water and open up the hot water..........the hot water heater will also start heating what little water is in the tank. It's gotta be a bad thing to heat up a mostly empty tank. 1. should i leave the gas turned off while it's filling?
2. should i use pipe dope or teflon tape on the gas line threads when i reconnect the gas?

[househelper]

Correct, don't turn on the gas until the tank is full. Use a Teflon based pipe dope, not tape. Check for leaks using a soap solution (kid's bubble mix works well).

[amp]

great. Thanks. I've got some leak detecting liquid.......it's fancy blue soapy water. it's great for hot water heaters, gas-tite connections, etc. Thanks again.

[gc717]

I see the danger from a valve on the hot side, but if a stop valve was installed on the hot water side (with a big red warning tag or the like hanging offit), should the expansion tank be installed:

1. between the "hot" stop valve and the hot water tank, or
2. on the cold supply line to the hot water tank?

The reason I ask is because I'm considering installing two 40 gallon natural gas hot water tanks to be plumbed in parallel, and it would seem convenient to be able to isolate one of the two hot water tanks completely for servicing. I would of course turn off the tank to be services, including the natural gas supply to the tank before servicing.

Or is it just much simpler and safer to only install stop valves on the cold supply water lines to the two tanks, and just drain off all the hot water in the house and shut down both HWT's (including gas supply) before doing servicing on one of the two tanks. Helpful suggestions/explanations much appreciated. Thanks.

Do not add a valve on your hot water side of the heater unless your going to add an expansion tank before the valve. As water gets hot, it expands and if someone closes the valve by mistake, you could burst your tank. You should only have a valve on your cold water line going into the water heater.

When you drain your tank, you might get a little siphon of you lines, but that is nothing you should be worried about. When you turn off the cold water inlet to the water heater, crack open a hot water faucet somewhere in the house to release pressure and to make an air vent to drain your hot water heater faster. Install your new heater, check for leaks, and bleed the hot water lines of air and you should be good to go.

[AllanJ]

Open one or two hot water faucets in the house wide to make the tank drain faster.

Trying to refill the tank using a garden hose spigot and the tank's drain valve is slower than closing the drain valve and letting the tank fill via the normal cold supply.

Do not turn on the gas or electricity until the tank is full, as evidenced by water is running freely for awhile from a hot water faucet upstairs.

I'm surprised that not putting a water heater shutoff on the hot water outlet improves safety. With all faucets closed, there is nowhere in the hot water network for water to expand into. The relief valve on the tank should open to prevent the tank from bursting due to an overtemperature or an overpressure condition. Each tank in a multiple tank installation must have its own relief valve in the socket provided.

Do not have a shutoff valve or any other gadget such as a check valve between the water heater and its expansion tank. Aside from this it really makes no difference whether the expansion tank is on the cold side or the hot side.