# How to convert a 500g propane tank to a Storage tank



## Bj1234 (Jan 16, 2016)

Hi all -
I have searched through the topics about  building/converting propane tanks into hot water storage tanks for wood boilers, I'll start reading ones comments and get lost cause topics sometimes go sidewyas. 

So I was hoping a few of the experienced guys can post thier "directions" on converting( 1) 500g propane tank into storage, then how to add a second later. Including size pipe recommendations, do we put a heat exchanger coil inside, to their favorate websites to buy the parts from, and how does the water heat/move through such a big tank. Since this is for new "do it your selfers", simple and easy would be appreciated.
Now If i missed a topic on this then I'm sorry, and hope someone would post the link here. 
Thanks!


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## maple1 (Jan 16, 2016)

It's a simple thing really. No coils. Just in & out fittings on top & bottom you can thread pipe into. Mine are 1-1/4", same as boiler tappings & near boiler piping. If you pump water in (or out) one fitting, it has to come out (or in) the other one. It's just a matter of putting the tank in a loop in series - broadly speaking. There are some intricacies in getting flows the way you'd want when also considering how your loads get piped in too - depending on the whole system layout. Check out the recent 'simplest pressurized storage revisited' thread - think all the basic bases are covered there, with diagrams & good broad discussion.


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## Bj1234 (Jan 16, 2016)

I was wondering about the coils. So it's a no on the coils... alright.. now it dosent seem as hard as I thought. I thought I had to run,coils in the tank.. thanks for the thread. I had a feeling I'd miss a thread, couldn't be the only one overthinking this....thanks


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## huffdawg (Jan 16, 2016)

Here's a pic of my tank mods.


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## JohnDolz (Jan 16, 2016)

huffdawg said:


> Here's a pic of my tank mods.
> 
> 
> 
> ...


Here is 1000 gallons, horizontal. Low ceilings but if I had to do it over again I would spend more time researching how I moght do it with vertical tanks.


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## JohnDolz (Jan 16, 2016)

JohnDolz said:


> Here is 1000 gallons, horizontal. Low ceilings but if I had to do it over again I would spend more time researching how I moght do it with vertical tanks.
> 
> View attachment 172142


Brain Crawford made these tanks for me. I should have mentioned his approach was to pipe from the top of the lower tank but there is a pipe inside the tank to pull from the bottom. If I had to guess I would say Brian read some threads here about water disturbance and went with this approach to minimize water disruption/stratification.


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## Bj1234 (Jan 16, 2016)

Nice set up guys... huffdawg , your pic easily show the pipes.. so the bottom is the (out )as In to the house...and the top is the hot(in) from the boiler? 
And what is the pipe at the very top that is cut of by the picture?


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## JohnDolz (Jan 16, 2016)

Bj1234 said:


> Nice set up guys... huffdawg , your pic easily show the pipes.. so the bottom is the (out )as In to the house...and the top is the hot(in) from the boiler?
> And what is the pipe at the very top that is cut of by the picture?


Take a look at the link below and it will give you a TON of info. But the top comes from the boiler and also supplies the house. Bottom is return to the tank and supply to the boiler.

http://www.nyserda.ny.gov/-/media/Files/EERP/Renewables/Biomass/biomass-hydronics-training.pdf


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## huffdawg (Jan 16, 2016)

The pipe at the top is an air vent .


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## Bj1234 (Jan 16, 2016)

Wow , different then what I thought..  thanks for the link....checking it out now..


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## JohnDolz (Jan 16, 2016)

huffdawg said:


> Here's a pic of my tank mods.
> 
> 
> 
> ...


I notice that you are going up with your return pipe (mine is also plumbed this way). I did a lot of reading this year and learned that the recommended setup for my loading pump is to have the return pipe be at the same low level as where it enters my loading pump. The idea is that if power ever goes out the system will then just have a gravity fed loop to keep the boiler from overheating. My thoughts are to redo it this way in the spring (I have some other plumbing that needs to be done), wondering what you think about this and why you chose to go up with that pipe?


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## huffdawg (Jan 16, 2016)

The storage tank supply and return attach to a buffer tank . Primary secondary  set up..


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## JohnDolz (Jan 16, 2016)

huffdawg said:


> The storage tank supply and return attach to a buffer tank . Primary secondary  set up..


OK thanks. I am going straight to/from my boiler.


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## Bob Rohr (Jan 16, 2016)

Here is a link to some additional info.
If at all possible mount the tank vertically, side ports, and consider the Two Pipe method for connecting.

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_17_na.pdf


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## maple1 (Jan 16, 2016)

Bj1234 said:


> Wow , different then what I thought..  thanks for the link....checking it out now..



More info & pics of my setup are in my install thread linked in my sig. My first piece of advice would be to get any tank welding done by a pro.


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## huffdawg (Jan 16, 2016)

Bob Rohr said:


> Here is a link to some additional info.
> If at all possible mount the tank vertically, side ports, and consider the Two Pipe method for connecting.
> 
> http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_17_na.pdf



Does the two pipe method have to  have the  pipe connections for the heat loads close to the storage tank?

Edit:  Found the answer in the link:

When using a 2-pipe confi guration, it is important to
keep the tees connecting to the load piping as close to
the tank as possible. The header piping between these
tees and the tank should also be generously sized to
reduce head loss to almost zero. Thus, the piping that
the heat source circuit and the load circuit share in
common has very low head loss, as illustrated in Figure
3-5. This ensures excellent hydraulic separation

It doesn't really say why Bob , how far would be too far from the storage tank?


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## huffdawg (Jan 17, 2016)

JohnDolz said:


> I notice that you are going up with your return pipe (mine is also plumbed this way). I did a lot of reading this year and learned that the recommended setup for my loading pump is to have the return pipe be at the same low level as where it enters my loading pump. The idea is that if power ever goes out the system will then just have a gravity fed loop to keep the boiler from overheating. My thoughts are to redo it this way in the spring (I have some other plumbing that needs to be done), wondering what you think about this and why you chose to go up with that pipe?



I  have a stby generator ready for just that reason.My Storage tanks are about 30ft away from the boiler in a separate room, to keep the return pipe low I would have had to run the pipe in front of the boiler room door


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## Kristen (Jan 17, 2016)

My boiler has a connection to the mains water. Not quite sure how it is plumbed, but in the event of overheat the valve to the (cold) mains water opens and hot water / steam! is flushed to a tundish, and from there to the drain.  We had a power cut last week in mid-Burn so I know that it is working


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## woodsmaster (Jan 17, 2016)

JohnDolz said:


> I notice that you are going up with your return pipe (mine is also plumbed this way). I did a lot of reading this year and learned that the recommended setup for my loading pump is to have the return pipe be at the same low level as where it enters my loading pump. The idea is that if power ever goes out the system will then just have a gravity fed loop to keep the boiler from overheating. My thoughts are to redo it this way in the spring (I have some other plumbing that needs to be done), wondering what you think about this and why you chose to go up with that pipe?


 
 I have mine plumbed similar to huffdawgs, but my return is at about the same level as the pump and it does thermosiphen enough to keep boiler from overheating in a no power situation.


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## Bob Rohr (Jan 17, 2016)

huffdawg said:


> Does the two pipe method have to  have the  pipe connections for the heat loads close to the storage tank?
> 
> Edit:  Found the answer in the link:
> 
> ...




That short, fat section of piping becomes your hydraulic separator.  Keeping it close and sized large assures the pumps do not interfere with one another, just as a hydraulic separator does.  You don't want any of the pumps causing un-wanted flow in the others.


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## huffdawg (Jan 17, 2016)

Bob Rohr said:


> That short, fat section of piping becomes your hydraulic separator.  Keeping it close and sized large assures the pumps do not interfere with one another, just as a hydraulic separator does.  You don't want any of the pumps causing un-wanted flow in the others.



. I was thinking of replumbing to the 2 pipe system so if the the storage tanks are already plumbed 1-1/4" and the boiler loop is 1-1/4 it wouldn't work without that pipe reduction? I was going to t in on the horizontal copper just before the vertcal run of black iron pipe on my tanks with 1-1/4 for the primary loop feeding the heat loads.
.


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## Bob Rohr (Jan 18, 2016)

what are the combined flowrates in that section?  ideally that section is sized so flow velocity with all pumps running is below 2 fps.


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## huffdawg (Jan 18, 2016)

I don't have flow meter inline. All I can tell you is , it is all 1-1/4 being fed by a 15/58 grundfos.


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## Bj1234 (Jan 24, 2016)

Can someone tell me ur thoughts...

If you guys had the space, what would be better, installing( 1 )1000gal storage tank horizontally OR installing (2)500gal tanks.side by side vertically?


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## ewdudley (Jan 24, 2016)

Bj1234 said:


> Can someone tell me ur thoughts...
> 
> If you guys had the space, what would be better, installing( 1 )1000gal storage tank horizontally OR installing (2)500gal tanks.side by side vertically?


Vertical has certain advantages, but they are not overwhelming advantages.

Both vertical and horizontal will stratify effectively, especially if horizontal ports, internal riser and dip tubes, diffusers, or internal elbows are used to minimize vertical jetting.

Personally, if I had the space, I would place a 1000 tank horizontally up on some sort of superstructure so I could use all the space below it.  The boiler, plumbing, expansion tank, and a cord or so of wood could all fit below nicely.

You would likely prefer some other arrangement, but my point is that what matters is how best to make use of the space available in your own particular situation, not the question of horizontal vs. vertical.

(If you do go vertical, note that if you use horizontal ports from the sides of the tank, *all* the volume above the upper port and all the volume below the lower port *will be lost* for heat storage.  To avoid this design defect you need to use an internal riser tube to inject or draw hot water from the top of the tank, and likewise you need to use an internal dip tube for the bottom of the tank. 

Or you can use ports at the top and bottom of the tank, perhaps with diffusers or internal elbows, which works very well, but takes just that much more vertical space and is difficult to plumb, in my experience.)


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## Kristen (Jan 24, 2016)

I have two vertical tanks, because we could not "tip" a single tank due to ceiling height.

They are connected by a "snorkle" tube (purple arrow in photo below) from about 1/3rd down primary to top of secondary.  In effect the pair of tanks stratify like a single vertical tank - heat gradient from top of primary to bottom of secondary.

In Summer we turn off the snorkle tube so that we only use the Primary.  We only light the boiler occasionally, for the pool (which also has solar heating which is enough 85% of the summer), but we also have solar thermal on the primary store and that definitely cannot heat two tanks! but it keeps the top half of the Primary at 60C / 140F which is enough to heat the domestic hot water (we have a coil at the bottom of the primary to pre-heat the DHW and another at the top for final heat; the bottom coil will do all the work if the Primary is hot enough at the bottom, which prevents destratification, if that is not hot enough then the top coil does the remainder of the work).


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## jebatty (Jan 24, 2016)

ewdudley said:


> Vertical has certain advantages, but they are not overwhelming advantages.... Both vertical and horizontal will stratify effectively, especially if horizontal ports, internal riser and dip tubes, diffusers, or internal elbows are used to minimize vertical jetting.


 I have a horizontal 1000 gal tank and ewd is exactly correct. Pictures will explain more fully. Boiler supply to top end of tank about 6" down from top with about an 18" pipe extension in the tank to direct hot supply water across the top of the tank. Boiler return is from the bottom of the tank at the same end, about 6" up from the bottom. System supply is from top of tank near the middle and system return is to bottom of tank near the middle via a diptube.



> Personally, if I had the space, I would place a 1000 tank horizontally up on some sort of superstructure so I could use all the space below it. The boiler, plumbing, expansion tank, and a cord or so of wood could all fit below nicely.... You would likely prefer some other arrangement, but my point is that what matters is how best to make use of the space available in your own particular situation, not the question of horizontal vs. vertical..


 True again, except that I boxed in my tank and fully use all the space above for storage. Much easier than trying to support a 1000 lb tank with 8,000+ lbs of water off the floor.



> If you do go vertical, note that if you use horizontal ports from the sides of the tank, *all* the volume above the upper port and all the volume below the lower port *will be lost* for heat storage. To avoid this design defect you need to use an internal riser tube to inject or draw hot water from the top of the tank, and likewise you need to use an internal dip tube for the bottom of the tank.


 This also can happen with a horizontal tank. My tank boiler return leaves about 6" of "dead" water below the return fitting, and this essentially does not heat when the tank is charged. The good news is that there isn't much water in this 6" of space, but also my system return at the middle of the tank via a diptube to the bottom does direct warm return water to the bottom of the tank and recovers some of this dead space volume.

Pictures: #1689 - tank in position in my shop
#1689 - welded fitting on the tank
#1695 - tank with boiler supply/return fittings
#1694 - tank with system supply/return fittings
#1705 - tank fully boxed in the raw
#1892 - tank finished boxing in, end with boiler
#1865 - tank finished end
#1815 - tank finished side view, with mural, storage above the tank


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## Bj1234 (Jan 24, 2016)

Thanks for all the pics everyone...pictures can tell someone so much... jebbatty- I might get back with you another time to pic your brain about your set up when i get to that point. Basically regarding the top of your tank. I thought in and out were all positioned on the sides but you have pipe and gauges on top of your tank to... is that because 1000gallon tanks are so long that you need to have some hot boiler water coming  into the tank from the middle due to the leangth?


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## maple1 (Jan 24, 2016)

I don't know if you checked out my install thread or not, but here are a couple pics from it, of my tanks.

This one is after I got them home from the welder. The one on the right is rolled over a bit, the top tank inlet for incoming boiler supply (or outgoing load supply) is at the 2:00 position there, roughly. Bottom outlet to boiler return (or incoming load return) is at the bottom of the tank on the left. (Tank in foreground is for expansion).






This one is the other ends, after I got them painted & stacked and most preliminary fittings in, just before I rolled them inside. They aren't hooked together yet, I did that after I got them parked, but you can see the fittings for it in the middle.


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## Bj1234 (Jan 24, 2016)

Maple1..... I did see your threads, very nice.. does the bottom tank have the open inlets on top of the tank to, just like the top tank does?..

 or does the bottom tank(on the sides) have 1 side in and 1 side out only..


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## maple1 (Jan 25, 2016)

Each tank has an outlet top and bottom, but on opposite ends. Then they're oriented so the top outlet of the bottom tank is on same end as the bottom outlet of top tank - per the last pic. Those get connected together (the 'run around' end, just connects the tanks) - basically makes them one tank. Fittings that would be on the other end of that last pic are top & bottom, that's where water enters & leaves the taks. Very simple.

There are also a couple of other small fittings (1/2 or 3/4, forget now) on each end top & bottom, for drain & vent purposes - can see the drains in the last pic. And I also have a couple of plugged holes on the centre top of the top tank that I could tap into in the future if I wanted.


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