Water heater tempering tank question

[Wisneaky]

Not the best picture, but I'm hoping if someone can tell me if this will work. I have one water heater set up as a tempering tank which then flows into my gas water heater and from there feeds my house. Can I run a pipe connecting both drains together to circulate the water around both tanks? Would I need to install a pump in the line if I did this or would the hot and cold water circulate by itself?

 

[woodgeek]

If you had two pipes like that and no pump, you would effectively double your hot water capacity.

Remember that HW tanks stratify, cold water enters and settles onto the bottom (often via an internal dip tube). The hottest water is on the top, and exits from there. This is intentional, if it was well mixed, then the temp (with no fire) would gradually fall as the water was depleted. Instead (with no fire) the cold water just pushes the hot out the top, and there is a relatively sharp interface between the two....when it reaches the top the temp falls quickly.

Your system of two tubes would allow the two tanks stratification interface to balance at the same height. Double the HW capacity.

Imagine one tank full of oil and one with water, after you open the two pipes, it would readjust until each tank had water on the bottom and oil on the top.

If you want a tempering tank (uninsulated, warms from space heat) then you would feed it tap water, and connect its out to the in of the gas heater.

If you circulated hot water with a pump between the two tanks, you would (i) have to run the pump (ii) double your parasitic losses (or more if the left tank is uninsulated) and (iii) the gas unit might act weird and deliver inconsistent temps due to the lack of stratification.

 

[Wisneaky]

If you had two pipes like that and no pump, you would effectively double your hot water capacity.

Remember that HW tanks stratify, cold water enters and settles onto the bottom (often via an internal dip tube). The hottest water is on the top, and exits from there. This is intentional, if it was well mixed, then the temp (with no fire) would gradually fall as the water was depleted. Instead (with no fire) the cold water just pushes the hot out the top, and there is a relatively sharp interface between the two....when it reaches the top the temp falls quickly.

Your system of two tubes would allow the two tanks stratification interface to balance at the same height. Double the HW capacity.

Imagine one tank full of oil and one with water, after you open the two pipes, it would readjust until each tank had water on the bottom and oil on the top.

If you want a tempering tank (uninsulated, warms from space heat) then you would feed it tap water, and connect its out to the in of the gas heater.

If you circulated hot water with a pump between the two tanks, you would (i) have to run the pump (ii) double your parasitic losses (or more if the left tank is uninsulated) and (iii) the gas unit might act weird and deliver inconsistent temps due to the lack of stratification.

Okay so what your saying is I can just plumb in the bottom line and I should be good to go? I thought it would work, but I wanted to make sure.

 

[woodgeek]

With a tempering tank you usually would do it as drawn, without the drains connected.

What are you trying to achieve?

 

[Wisneaky]

With a tempering tank you usually would do it as drawn, without the drains connected.

What are you trying to achieve?

Trying to double the capacity.

 

[Wisneaky]

I have it hooked up now without the drains connected. No real change though. My incoming water is rather cold. The first tank is insulated though so that is probably why its not helping. I'd like to hook the drains up if it will work.

 

[woodgeek]

The dip tube in the gas heater makes it more complicated, but prob harmless to try.

 

[Wisneaky]

The dip tube in the gas heater makes it more complicated, but prob harmless to try.

Thanks for your help.

 

[DougA]

If you just want to pre-warm the water coming in from a cold well, would you not be better to run some copper pipe on the ceiling of your warm basement (assuming it's in the basement) prior to the gas HW heater? If you are using the tempering tank without a heater in it, the tank will take forever to bring the water up to room temperature because it's a huge mass of water with little exposure to warm air. The downside is that your pipes will probably drip condensation in the warm, humid air in the summer.

 

[STIHLY DAN]

Are you using hot h2o of caddy? Tempering tank is an easy install.

 

[Wisneaky]

Are you using hot h2o of caddy? Tempering tank is an easy install.

I haven't bought a coil yet. I was just trying to see if this would work. The coil will be a later add on.

 

[maple1]

I'm not sure this will do anything much without a pump.

The line from tank to tank at the top is looking to me like it would act as a heat trap.

 

[Circus]

Trying to double the capacity.

Forget the term "tempering tank", it's just confussing. If you want to double the amount of stored hot water, insulate, remove any check valves or dip tubes and tap the hot water (hot out) from your upper crossover. Plug the present "hot out".

Make sure there's a dip tube at the supply (cold in).

 

[Wisneaky]

Forget the term "tempering tank", it's just confussing. If you want to double the amount of stored hot water, insulate, remove any check valves or dip tubes and tap the hot water (hot out) from your upper crossover. Plug the present "hot out".

Make sure there's a dip tube at the supply (cold in).

The bottom drain lines would still have to be hooked up together or the water would not circulate, right?

 

[Circus]

The bottom drain lines would still have to be hooked up together or the water would not circulate, right?

Yea, you could also have the cold supply tapped into the lower crossover. Plug the original inlet.
The thermosyphoning might work a bit better if the auxiliary tank was a inch or so higher than the water heater.
You should keep some means of draining the tanks.

 

[Wisneaky]

Yea, you could also have the cold supply tapped into the lower crossover. Plug the original inlet.
The thermosyphoning might work a bit better if the auxiliary tank was a inch or so higher than the water heater.
You should keep some means of draining the tanks.

Yeah I was going to put a tee in the bottom line with a shut off to use as a drain. I'll mess around with it this coming weekend.

 

[Circus]

Yeah I was going to put a tee in the bottom line with a shut off to use as a drain. I'll mess around with it this coming weekend.

In Wisconsin water heaters fill up with sediment and sometimes you need to poke a rod into the bottom drain to get it out. Ever hear a water heater pop and girgle? It's easier to do if you can spoke the rod staight through the drain (ball valve), pipe and into the waterheater.