Extrol Mounting

rich pickering

Gotta remember that air has about 20% o2 that reacts quickly with any iron and is consumed. The other 80% is nitrogen which won't cause corrosion, but it can still airlock a system.

And many BIG tanks are floor mounted with the fittings on the bottom. It's the only way you can drain them.

Unknown

Extrol Mounting

Hey everyone I need a little learning here.

I've seen a growing trend of small (non base mounted)Extrol "style" Expansion Tanks (and small domestic hot water expansion tanks) mounted on their side and even upside down (threads pointing down).

I was always taught that these tanks should be (a) mounted on the air scoop or air remover, and (b) should be pointed with threads up so that air can not collect in the water side of the expansion tank.

If air is trapped on the water side there becomes a problem. Where there is air there can be no water hence reducing the capacity of the tank and causing early corrosion.

So I looked up the installation instructions on Amtrols website and sure enough it states to mount as show and they show tanks mounted threads up as I was taught.

I mentioned this "horiz" mounting to a manufacture of pre-built systems and asked them to explain it to me. The response was they did this to "save spaca" BUT decided to change their manufacturing ways ways immediately and mount the tanks "as shown" from that point on.

Can anyone explain why you would mount the Extrol style tank horizontally or upside down??? Is this being taught somewhere??

Thanks
'
Steve

chris_93

tank mounting

I recently wondered the same thing. I was always taught to "hang it". I think the manuf. all have different specs. I recently checked watts webpage for there et 30 tanks. and it says the tank can mount in any position. We all know they work in any position, but is mounting it upside down or horiz. causing premature failure- I would love to know too.
here is the link,
http://www.watts.com/pdf/1910715.pdf

Paul Rohrs_4

Modern Hydronic Heating - Chapter 12

Siggy's 1st edition. Chapter 12 on expansion tanks gives is a lot of good info on Page 383.

1. Since the diaphragm separates the fluid from the air, the air volume is protected against reabsorption by the fluid. Diaphragm-type expansion tanks do not have to be periodically drained to prevent water logging.

2. By avoiding water logging, the possibility of accelerated corrosion caused by the addition of fresh water to make up for relief valve losses is no longer a factor.

3. The fact that the air volume can be pre-charged to match the static pressure of the system results in a significantly smaller and lighter tank compared to a standard expansion tank.

**4**. (Answering Wheels original questions)
Since the air is captive, the tank can be mounted in any position.

5. The special boiler and tank fittings required with standard expansion tanks are no longer needed.

__________________________________________________________

If I understand your concerns correctly, I would say that the line leading to the expansion tank should be purged so that air is not bound in the tank so that the full complement of water volume fills the tank (against the bladder) and does not inhibit the expansion of water as it heats.

Hope this helps.

Paul

Paul Rohrs_7

The other thing I was thinking

was I can't tell you how many old style compression tanks I have seen without the correct air-trol type tank fittings. 40-50 year old systems with the original tank that are piped in black iron and MAYBE have a union on it. By default, with the initial fill and no airtrol type fitting the thing had to be air-bound, but the water as it heated only had 1 place to expand to. It had to displace the air in the tank by compressing it. Water and air in direct contact to steel and no catastrophic corrosion.

Just another thought.

Paul

Abro

Siggy says...

2nd Edition Pg 466

He talks about how trapped air bubbles "will corrode the steel tank sheel" and concludes:

"These factors support the author's recommendation that small diaphram-type expansion tanks should only be mounted vertically with their inlet connection at the top."

He also advocates separating the tank from the tap-in point with several feet of piping to reduce tank warming which reduces expansion capacity and also warns that the lower the tank is mounted the more static pressure it will have which will also reduce its expansion capacity.

Unknown

So

screwing it (up) into the bottom of an AS means its OK?

Dave

Unknown

1ST EDITION DIFFERS FROM SECOND EDITION????

Uni & Paul,

We seem to have a conflict of versions here. I obviously have been taught for many years what is shown in Edition 2.

crap, now what do I teach to my students!

BTW - screwing the tank into your AS works great. It appears as though Siggy suggests a short pipe though.

wheels

hot_rod

Agree with the manufacturers

advice to mount them threads up.

I have been guilty of sideways mounting, at least 20 years worth that I can recall. I have no evidence that the life expectancy is any shorter on their side, does anyone else?

20 years plus out of a very thin tin container, for about 40 bucks pencils out well for me. I've had some boilers, for much more money, fail in much less time. Haven't we all.

The ONLY chronic expansion tank failure I have noted is on non barrier tube systems, and acidic ph systems.

The problem is, the industry lacks a good, inexpensive, multi mount expansion tank bracket. I'm working on that...

This idea pictured below is plenty stout, has gauge, tank, fill, and drain valve openings. Choice of colors

hot rod

Unknown

base mounted tanks

Rich,

As I see it, base mounted tanks always have their supply come down to them at a far distance and then the pipe makes a u bend into the tank. This alone usually keeps the air from making it there. PLus you are installing at "as shown" :-)

Just a theory,

wheels

Joe Billow_6

Brass air manifold. I have used them for mounting tanks. They look like the cross you posted but have a mount on them. I will get a pic.

Brian_18

Manufacturer's Recommendations

I also agree to install a product to manufacturer's recommendations. It seems Amtrol says to install their product ONLY vertical. Watts, says their product can be installed Vert., or Horizontal.

http://www.watts.com/pdf/1915323.pdf

So, maybe this argument has more to do with individual product design, rather than general plumbing physics.

Unknown

the preferred method

Brian,

The Watts potable and heating expansion tank installation instructions do indeed state that you can mount their tank verticle or horizontal, but their PREFERED METHOD is Verticle with threads pointing up.

Mmmm, I guess if you install the tank any which way you want it will work. Maybe if you install it in other ways besides the preferred method you will go through tanks more often..... mmmm. As a manufacture I would not argue this point.

I also see that Amtrol states NOT to install their tank in the joist bay like a standard expansion tank.

Steve

Unknown

We replace expansion tanks

on new installs that are mounted in every position , it really makes no difference in longevity . Not too long ago we had a # 15 that was sitting horizontally in a joist bay . Date code of 1979 with 5 psi in the tank after all those years .

After a buddy got 2 fingers badly hurt by being pinned between a waterlogged tank and a boiler ( tank was hanging down ) , I hardly ever pipe 'em that way anymore .

scrook_2

trapped air

Steve W. said: "if air is trapped on the water side there becomes a problem. Where there is air there can be no water hence reducing the capacity of the tank and causing early corrosion."

But if air (only a little bit as the pressurized diaphragm should be against the nipple end of the tank before installation) is trapped on the water side of the diaphragm, it would actually *increase* the capacity of the tank, slightly, as it would serve as a small additional air cushion above and beyond the air on the dry side of the diaphragm (at least until it goes into into solution w/ the water).

I imagine it would be preferable from a corrosion point of view to not have air trapped though, so can't disagree w/ Steve there.

In the real world there are places like Levitown where there may be little alternative to a horizontal (or up high, nipple down, on a dead ended riser), due to the size of cubby hole the boiler lives in, but one runs into manufacturer's warnings:

Amtrol and B&G, (but not Watts) warn to:
"Mount vertically only. Do not mount on dead-end pipe."

Alas, they don't state whether this is to prevent bending loads on the mounting nipple, corrosion at the water/trapped air interface, or other.

If I had to mount one horizontally I'd make sure it was WELL supported, and was a brand that didn't warn against non-vertical mount in the IO manual.

Also, on larger, floor standing bottom, fed commercial sized bladder tanks, how does the trapped air (granted minimal, that in the elbow and horizontal pipe out thru the skirt) above the water get out (other than by eventual solution into the water)?

Rob Blair

Waterlogged tank

I just found out last week what you were talking about first hand Ron. Had a waterlogged #30 hanging on an air eliminator over a Peerless Pinnacle. The system had glycol which added to the slipperyness. Tank fell through my one hand that I thought could support it, bounced back up off the Pinnacle hitting my middle finger and stoving it bad. Of course glycol was everywhere.

My friend told me that the good thing is that "You'll only do that once!".

I believe he is right!

Rob

heatboy_3

The only reason...........

......... I can think of is the neck of the tank is the weak point because of the least amount of metal. Any installation other than threads up will expose this area to added stress. The neck is almost sacrificial anode like and the potential of it breaking off if any corrosion is present causing a flood is much greater.

As far as any operational difference, there isn't any.

gerry gill

seems to me

that if the proper air charge is in the bladder, when the system is cool, the bladder will occupy 100% of the tank..

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Tony_23

Vertical up

That's how I strive to do it.

I always screw 'em into a ball valve for quick, easy replacement w/o the need for draining/bleeding the system. Can't imagine trying to remove one that's waterlogged if it's upside down.

My Dad also broke his finger trying to "catch" one that was mounted way too high and over the water heater.

scrook_2

Yes, if

the system pressure is (even slightly) below the bladder air pressure. e.g. system at 11 3/4 psi cold, bladder at 12 psi. (assuming you could read the two pressures to sufficient precision and with sufficient accuracy).

As a generality the bladder (and air) should fill the tank on a cold system, and in rough numbers the bladder/air will fill about 3/4's of the tank (so about 1/4 water) at about 21 psi for a 12 psi cold fill and 12 psi initial air pressure.

Also, when the tank is first installed, or any time the system pressure is reduced to zero to change out a part the bladder will also entirely fill the tank.

TGO_54

Changing waterlogged tanks (TGO)

Next time you run into one of these, punch a hole in the bottom and top of the tank and allow it to drain into a bucket before removing it.

The idea came to me after I smashed my fingers changing a full one ;-)

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