# Expansion tanks options?



## cjdave (Jan 22, 2012)

Ok, So some of you have seen my thread on stacking my 1000 gal propane tanks. So now I am working on getting all my system components together to start the install. That has lead me to expansion tanks. My system design calls for 2 Amtrol SX-160V's 86 gal volume 46 gal acceptance. So Correct me if I am wrong but the amount of usable water volume in these tanks is 46 gal? the other 40 gal is for the air bladder? SO the best price I have found on those tanks is just shy of $500 each :O ! So I am looking for options, I have seen Goosegunners thread on his Lp tank for expansion and this looks like a good option, is there any concerns with not having a bladder to separate the air from the water? If so could I charge with nitrogen or some other inert gas (if it is oxygen infiltration we are worried about?). goose, how is your setup working out? any problems or things you would have done different?
Has anyone else done a Lp tank or other tank (other than a purchased expansion tank) for there system? What about just a non bladder well tank? Or what is the difference between the well tanks (with bladder) and the tanks for heat systems?


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## Clarkbug (Jan 22, 2012)

I also needed a lot of expansion room, and I ended up with 3 Amtrol SX-60Vs.  Just mainfolded together to get my room for expansion.  That put me back just shy of $700.  

You can use a tank with no bladder in it, and there are several posts here about people who did just that.  I would say the only thing to do is to install a sight glass in it so you know when the air is getting re-absorbed into the water and can drain some water out of it.  Might end up being a non-issue for several years.  The nitrogen charge is an interesting idea, not sure how that would work out, but its a neat thought.  

Well bladder tanks arent typically rated to handle the heat of a hot water hydronic expansion tank.  So if something happens, they wont be held liable.  That said, someone had posted on here that you could probably still use them if you had them connected via some fin tube or something like that to make sure the expansion tanks never saw any heat.


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## lotawood (Jan 22, 2012)

I'm about to buy a sx-160v also or a hft-160v.  So I am interested also.  Best I can tell for a captive air tank , from a propane tank,  you use the amtrol fitting for expansion tanks.  I can't find that part at the moment.

Found it.  Airtrol ATFL or ATF bell and Gossett for a compression tank.


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## Donl (Jan 22, 2012)

I have been using a 50 gallon electric dhw tank someone threw out for the past few years with no problems. These tanks are readily available for free.


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## woodsmaster (Jan 22, 2012)

Here's one I made from a 124 propane tank. Paid $60.00 for the tank. Works great. Has a float gauge built in so
don't need a sight glass. just added the drain / inlet on the bottom and in air valve in an existing hole on the top.
Has a valve to shut off from the system on the other end of the pex for precharge / drain tank if ever need to. It's
stayed at the same water level since put in use.


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## stee6043 (Jan 22, 2012)

I really like some of the home-built expansion tanks I've seen on this site in the past year or so.  It's a great way to save a chunk of change.  But I will say that you can't beat the bladder tanks for ease of installation and use.  But it comes at a price.  I have (2) 60 gallon tanks on my system...


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## wood thing (Jan 23, 2012)

I,m using a 40 gal hot water tank and also a 40 gal amtrol  well tank w/bladder.  price was right.  Still looking for one more.  I have these charged with 15 psi.  So far so good.


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## Yankee (Jan 23, 2012)

Like Woodmaster, I used a 120 propane tank.  I removed the valve and fittings, installed plugs and a tee, and mounted it upside down on the flange.  I didn't have a hole in the bottom, so I drilled and tapped for a tee with shrader valve.  From the tees I ran a sight tube top to bottom.  I am plumbed into the bottom of my 1000 gallon propane tank at the return with about 10 feet of 3/4 tube to the 120.  I never see any hot water in the 120 once I am up to temperature.  

Tom


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## RobC (Jan 23, 2012)

DIY has worked great, been in use for 3 years.
Rob


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## goosegunner (Jan 23, 2012)

cjdave said:
			
		

> Ok, So some of you have seen my thread on stacking my 1000 gal propane tanks. So now I am working on getting all my system components together to start the install. That has lead me to expansion tanks. My system design calls for 2 Amtrol SX-160V's 86 gal volume 46 gal acceptance. So Correct me if I am wrong but the amount of usable water volume in these tanks is 46 gal? the other 40 gal is for the air bladder? SO the best price I have found on those tanks is just shy of $500 each :O ! So I am looking for options, I have seen Goosegunners thread on his Lp tank for expansion and this looks like a good option, is there any concerns with not having a bladder to separate the air from the water? If so could I charge with nitrogen or some other inert gas (if it is oxygen infiltration we are worried about?). goose, how is your setup working out? any problems or things you would have done different?
> Has anyone else done a Lp tank or other tank (other than a purchased expansion tank) for there system? What about just a non bladder well tank? Or what is the difference between the well tanks (with bladder) and the tanks for heat systems?



Mine seems to be working so far. My thill float has failed to float anymore. I had cut the bottom off a little and it may have taken on water, it was a plastic float.

One thing I don't understand is that my pressure seems to a little lower than initial. Maybe that indicates a problem with air absorption?

gg


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## cjdave (Jan 23, 2012)

It's good to see so many home brew setups. I'm having a hard time coming up with a 200-250 gal tank so it might come down to a couple smaller tanks. I am thinking about using 2 tanks 1 as a water acceptance tank and the second as the air resevoir. So basicly water in to the bottom of the first tank and air line from the top of that tank to the bottom of the second tank. Might even go with nitrogen charge, I have to do some research on that.


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## thecontrolguy (Jan 23, 2012)

If you are using a non-bladder tank you SHOULD be using oxygen-scavenging chemicals with inhibitors like molybdate or sulfate- based chemicals. When you put the tank into service, first fill and then flush to get rid of particulates, and crud, then fill all the way to top with your final chemical water.  This is before charging with air.  Let sit for a day or more to plate the insides of the tank with inhibitors to protect the metal.  Then, pressure up with air until the level is correct and set the initial system pressure.  Adjust pressure / level after when heat is added.  I see many systems that add the make-up water directly to the expansion-tank loop and thus bring fresh untreated wated into the tank and cause corrosion and premature failure.  Good luck.


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## huffdawg (Jan 23, 2012)

stee6043 said:
			
		

> I really like some of the home-built expansion tanks I've seen on this site in the past year or so.  It's a great way to save a chunk of change.  But I will say that you can't beat the bladder tanks for ease of installation and use.  But it comes at a price.  I have (2) 60 gallon tanks on my system...



Stee what sort of pressure you running at when your storage is 195 Â°F 
Ya I agree I should of made my own expansion . Cost me over a g note for two 62 gal extrol exp. tanks :ahhh: 

Huff .


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## RobC (Jan 23, 2012)

One thing I don't understand is that my pressure seems to a little lower than initial. Maybe that indicates a problem with air absorption?

gg[/quote]
I have a fluctuation in charge too. I had attributed it to the size of the system and the fact the system fluctuates with swings in temp in storage. In the winter I run between 150+ or- to 180+ and see some fluctuation. In the summer when I let it go down to 120 or so my pressure really drops. My system is all on 1 floor level so I don't thinks it's an issue for DHW in summer with low pressure before I recharge.


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## goosegunner (Jan 23, 2012)

RobC said:
			
		

> One thing I don't understand is that my pressure seems to a little lower than initial. Maybe that indicates a problem with air absorption?
> 
> gg


I have a fluctuation in charge too. I had attributed it to the size of the system and the fact the system fluctuates with swings in temp in storage. In the winter I run between 150+ or- to 180+ and see some fluctuation. In the summer when I let it go down to 120 or so my pressure really drops. My system is all on 1 floor level so I don't thinks it's an issue for DHW in summer with low pressure before I recharge.[/quote]

Right now I have been running my system

Temp  144-185

With these temps pressure will range from

14-21psi

Does that seem right?

I haven't taked it to 189 for a while but when I did it was at 25 psi. I did let out probably 8 gallons of water because I thought 25 was a little high. 

gg


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## stee6043 (Jan 23, 2012)

huffdawg said:
			
		

> stee6043 said:
> 
> 
> 
> ...



I will push 28psi at full temp, 190+ top to bottom on both of my tanks.  My pressure is 12-13 psi with 60 degree water top to bottom in the fall before I fire up.  I don't recall the Amtrol model numbers I'm running but I believe they are just over 40 gallon acceptance, each.  They could be 60 acceptance....but I don't really recall!


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## Donl (Jan 23, 2012)

I have approx 600 gallons of water in my system.  I use a small bladder expansion tank ( I think about 7 gallons acceptance) and a 50 gallon DHW tank. The pressure varies between 14 -15 lbs at 140 degrees and 25-27 lbs at about 200 degrees.  The first year I ran this I would exceed 30 lbs when running close to 200 degrees. I did the following to lower the operating pressure:

1. start when system is cold (50 degress approx)
2.. shut valve to 50 gallon expansion tank and drain if it contains any water.
3.  pressurize system to 12 psi via makeup water port.
4. pressurize 50 gallon expansion tank with compressed air to 12 lbs psi.
5. Open shut off valve to 50 gallon expansion tank.
6. You are good to go for another year. 
7. repeat next fall. (The expansion tank will have less than a gallon of water in it that must be drained)

I left the sacrificial anode rod in the expansion tank. I don't know if this was a good idea or not. I am assuming that this rod will help reduce the effect oxygen has on the overall system.


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## RobC (Jan 24, 2012)

I havenâ€™t taked it to 189 for a while but when I did it was at 25 psi. I did let out probably 8 gallons of water because I thought 25 was a little high.

gg

I remember originally changing water level and air pressures in expansion tank. Then I realized that it was acting about the same as if I had did nothing so, I left well enough alone. 
Last summer I did add air to the expansion tank because my system pressure was really low, when I fire every 3rd or 4th day. ( have had a couple auto vents leak ) Since then no change in low temp PSI reading. I run my system with the auto-fill line shut off so any changes would be noticeable.
Rob


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## goosegunner (Jan 24, 2012)

My auto fill is open but my system has not dropped below 12 psi so I don't believe it would add any water.  At this point it is hard to know what to add. Once I let system cool I should know how much air to add.

Gg


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## cjdave (Jan 24, 2012)

Having a hard time finding a 250 gal pressure tank around here, the ones i have found are stupid expensive. So it's coming down to several smaller tanks, I can buy 100# propane tanks all day long at $30-50. Thinking about getting 6 or so of them (only hold aprox 23 gal). or I have been looking at amtrol's site and found some confusing data. There are 3 tanks that show the same acceptance volume but the total tank volume is not the same. How is this possible?
here are the numbers

             total volume       Acceptance
SX-90V          44                     34.0         

SX-110V        62                     34.0 

SX-130V       81                      34.0 

SX-160V       86                      46.0

How is it possible that the sx-90, 110, and 130 have the same acceptance but such a big difference in tank volume?


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## ewdudley (Jan 24, 2012)

cjdave said:
			
		

> How is it possible that the sx-90, 110, and 130 have the same acceptance but such a big difference in tank volume?



Acceptance is merely how much water can enter the tank before the bladder reaches its stretch limit.  The tanks all have the same bladder sub-assembly inside tanks of different sizes.

As long as acceptance is greater than about 4% of system volume, the bladder is big enough.

But that doesn't mean the tank is big enough, since it is the tank size, not the acceptance volume, that determines the pressure rise.

--ewd


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## RobC (Jan 24, 2012)

cjdave said:
			
		

> Having a hard time finding a 250 gal pressure tank around here, the ones i have found are stupid expensive. So it's coming down to several smaller tanks, I can buy 100# propane tanks all day long at $30-50. Thinking about getting 6 or so of them (only hold aprox 23 gal). or I have been looking at amtrol's site and found some confusing data. There are 3 tanks that show the same acceptance volume but the total tank volume is not the same. How is this possible?
> here are the numbers
> 
> total volume       Acceptance
> ...



See if you can find a 100 Gallon propane tank. The guys that have the 100 LBS one should be able to get you one. Or Craigslist.


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## cjdave (Feb 10, 2012)

Ok, so I picked up a really nice 80 gal vertical air compressor tank. And a old millitary aircraft fuel drop tank (you guys are going to love that one) going to use the 80 as the water tank and the drop tank as a air res. Might have to polish the drop tank and hang it from the ceiling (its aluminum) just for the novelty factor... I will get some pics as soon as I get them in the shop.


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## goosegunner (Feb 10, 2012)

cjdave said:
			
		

> Ok, so I picked up a really nice 80 gal vertical air compressor tank. And a old millitary aircraft fuel drop tank (you guys are going to love that one) going to use the 80 as the water tank and the drop tank as a air res. Might have to polish the drop tank and hang it from the ceiling (its aluminum) just for the novelty factor... I will get some pics as soon as I get them in the shop.



What is air reserve?

Is that to vent air from the separator so it is not lost to atmosphere?

gg


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## cjdave (Feb 10, 2012)

basically instead of having a tank with air on top and water in the bottom, i am using the 80 gal tank for water acceptance and the air in the drop tank, only because I could not find a single tank big enough for both water acceptance and air. We will see how it works.... top of the 80 gal water tank connects to the bottom of the drop tank, schrader valve on top of the drop tank to charge with air...


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## goosegunner (Feb 10, 2012)

cjdave said:
			
		

> basically instead of having a tank with air on top and water in the bottom, i am using the 80 gal tank for water acceptance and the air in the drop tank, only because I could not find a single tank big enough for both water acceptance and air. We will see how it works.... top of the 80 gal water tank connects to the bottom of the drop tank, schrader valve on top of the drop tank to charge with air...



How much water are you going to put in the 80 gallon tank?

One thing I think would make an improvement on my Expansion tank is one of the Bell & Gosset valves that goes in the bottom to return air from the separator to the expansion tank.
Not sure where to get on with a long stem though.

gg


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## maple1 (Feb 10, 2012)

I'm guessing whatever amount of water that ends up in the 80 gallon tank will just be whatever enters it as the cold storage pressure equalizes with the pre- charged water pressure in the drop tank. Kind of just a two piece expansion tank.


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## cjdave (Feb 11, 2012)

maple1 said:
			
		

> I'm guessing whatever amount of water that ends up in the 80 gallon tank will just be whatever enters it as the cold storage pressure equalizes with the pre- charged water pressure in the drop tank. Kind of just a two piece expansion tank.


Yes that is what i am planning on happening. That brings me to a new question, how much air pressure should I pre charge with?


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## RobC (Feb 11, 2012)

As I recall when doing mine I just let it equalize with system pressure. My propane tank has a level gauge on it and it reads about 40%. After filling you may want to add some air but I wouldn't go overboard.


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## maple1 (Feb 11, 2012)

Assuming your system pressure when system is cold is to be around 12psi (a standard number), I would shut off both your 'extra' tanks from system with system at low system temp & 'extra' tanks empty, fill system (boiler, storage & distribution) with water to 12psi at low system temp, charge the two 'extra' tanks to 12psi of air, then open them to storage & start heating. If you start with less than 12psi in the 'extra' tanks at low system temp, then when you open them to the system water will flow in until pressure equalizes. That will reduce room left for expansion as system heats.


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## Donl (Feb 11, 2012)

maple1 said:
			
		

> Assuming your system pressure when system is cold is to be around 12psi (a standard number), I would shut off both your 'extra' tanks from system with system at low system temp & 'extra' tanks empty, fill system (boiler, storage & distribution) with water to 12psi at low system temp, charge the two 'extra' tanks to 12psi of air, then open them to storage & start heating. If you start with less than 12psi in the 'extra' tanks at low system temp, then when you open them to the system water will flow in until pressure equalizes. That will reduce room left for expansion as system heats.



Yes!


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