Okay so i turned on the pump and opened the hot & cold water valves in kitchen and bathroom sinks, and ran until all water stopped spitting out. I then went to the outside hot water tank compartment and removed the plug only to find that a significant amount (in the gallons) continued to pour out. so my question is why didnt the pump remove at least most of the water from the hot water tank?

I am thinking the outlet for the hot water is at the top of the tank.Hot water rises and cold sinks, so they probably do not have the outlet to close to the bottom of the tank.Thus when the hot water tap is open it will draw from the tank only down to the level of the outlet, thus leaving water in the tank until you open the drain at the bottom. Also when you open the drain you should open the relief valve also to allow air into the tank to help it drain.

The pump can only pump as long as the pump has water coming into it. Once air gets into it it doesn't do very well. Even if it did it could only pump out the water above the hot water outlet which is at the top of the heater.Better to set the bypass valves and then drain the heater. I use a hose to siphon what is left in the tank after it drains.

The water pump sucks from the Freshwater tank and pumps into the hot water heater. The pump keeps the hot water tank full, it doesn't empty it. You stopped getting water out of the faucets because the pump ran out of water from the freshwater tank.The only way to empty the hotwater tank is to drain it and that can be 6 or 10 gallons of water depending on your size.

Better to just open the drains on the water lines with the pump off. Open all the faucets inside and the water will drain out on it's own. Remove the drain plug on the water heater and let it drain. As mentioned the pump won't blow out the lines very well and certainly not the water heater.

Another way of looking it is the pump pushes water through the system. When the tank runs dry it mostly pushes air. It can't push enough air to drain the heater especially since the water heater discharge is at the top (hot water rises.)

draining hot water tank | Good Sam Community

20 Replies

GaryUT
Explorer II
Nov 06, 2013
thirtydaZe wrote:
If I may, can i piggy back on the topic and ask, is there a standard size to the plug for removal. I went out and did an on the storage location winterization saturday, and was unable to reach the plug with my wrench. I'll be needing a socket to reach.

Just thought I could catch a quick answer here.

When I was using the drain plug one of the ends of my star lug wrench was the correct size.

Gary
rseymour21
Explorer
Nov 05, 2013
Matt_Colie wrote:

(The valve in the toilet is a favorite ~45$ for the parts).

Matt

Thanks Matt, you know, I don't thin I've ever caught that one! Good one to keep in mind!:o
partsman01
Explorer
Nov 05, 2013
thestoloffs wrote:
I'd also insert instructions on opening the pressure relief valve or both a hot & cold faucet before removing the drain plug.

If the pressure isn't relieved before the drain plug is pulled, there could be a very rude unexpected shower forthcoming.

Not to mention that plug under pressure comes out like a shot, and it hurts, even the water comes out fast enough initially to hurt a bit.
Make sure all pressure is gone.
thestoloffs
Explorer
Nov 05, 2013
I'd also insert instructions on opening the pressure relief valve or both a hot & cold faucet before removing the drain plug.

If the pressure isn't relieved before the drain plug is pulled, there could be a very rude unexpected shower forthcoming.
TubaPete
Explorer
Nov 05, 2013
tenbear wrote:
thirtydaZe wrote:
If I may, can i piggy back on the topic and ask, is there a standard size to the plug for removal. I went out and did an on the storage location winterization saturday, and was unable to reach the plug with my wrench. I'll be needing a socket to reach.

Just thought I could catch a quick answer here.

I use a 7/8" wrench on mine. Don't know if all heaters are the same.

One I had was 1 1/8" so I would say they are not all the same.
thirtydaZe
Nomad
Nov 04, 2013
well thanks guys for the quick replies, sounds to be less standard than i was hoping.
tenbear
Explorer
Nov 04, 2013
thirtydaZe wrote:
If I may, can i piggy back on the topic and ask, is there a standard size to the plug for removal. I went out and did an on the storage location winterization saturday, and was unable to reach the plug with my wrench. I'll be needing a socket to reach.

Just thought I could catch a quick answer here.

I use a 7/8" wrench on mine. Don't know if all heaters are the same.
sign_man
Explorer
Nov 04, 2013
thirtydaZe wrote:
If I may, can i piggy back on the topic and ask, is there a standard size to the plug for removal. I went out and did an on the storage location winterization saturday, and was unable to reach the plug with my wrench. I'll be needing a socket to reach.

Just thought I could catch a quick answer here.

if i'm not mistaken i believe its a 3/4"
thirtydaZe
Nomad
Nov 04, 2013
If I may, can i piggy back on the topic and ask, is there a standard size to the plug for removal. I went out and did an on the storage location winterization saturday, and was unable to reach the plug with my wrench. I'll be needing a socket to reach.

Just thought I could catch a quick answer here.
tatest
Explorer II
Nov 04, 2013
I can drain my water heater using a low point drain in the HW line under the shower, by opening the pressure relief valve. It happens to be in the right place to siphon from the tank. Only a little water left when I remove the drain plug. This may not work for everybody, but there should be a low point drain somewhere in the hot water line.