Advice regarding replacing a compression tank with an expansion tank

tdi

My system is a Weil-McLain CG-6 Series 7 Natural Gas Boiler from 1981 with a circulator pump on return side of the boiler and a steel expansion tank tucked into the floor joist area above and the the left of the boiler (tight fit with iron and copper piping to 1920s radiators).

The expansion tank is likely 40 years old and has started leaking water at the tank end (side) along a welded seam. In reading various posts and online articles it appears that I may be better suited to replace and install an expansion tank.

Based upon sizing calculators, I arrive at this tank size, Extrol #90 Expansion Tank (14.0 Gal Volume).

With the circulator pump on the return side of the boiler, my understanding is that the expansion tank should be on the supply side of the circulator pump in a vertically downward position. Is this correct?

I can provide system photos if it helps.

Thank you in advance.

Jamie Hall

The expansion tank should be on the inlet side of the pump -- therefore, in your situation, on the return side of the boiler, before the inlet to the pump. So that part of your understanding is correct. As for orientation, they don't like to be on their sides. At all. But they can be mounted with the water connection vertically up or down, just so long as they are well supported (they are heavy).

EBEBRATT-Ed

What size or measurements do you have for the old tank? A size 90 bladder tank is a big tank. Oversizing is not an issue just more $$$

Make sure to check the air pressure in the new tank before installing it. Should be 12-15 psi

The best way is to put a valve in between the expansion tank and the system for future changes and to check the air pressure. Put a tee between the isolation valve and the expansion tank and put a drain valve or a plug into the tee.

If your relocating the tank the city water MU should be on the same side of the circulator that the expansion tank is connected to

tdi

@Jamie Hall Thank you for your feedback.
@EBEBRATT-Ed Thank you for your feedback. You asked:

EBEBRATT-Ed said:

What size or measurements do you have for the old tank? A size 90 bladder tank is a big tank.

The existing steel compression tank is approximately 26" long x 13" diameter which I calculate volume of about 15 gallons. Given the pricing difference between #60 and #90 and what the various sizing calculators recommend with the cast iron radiators, I opted for #90.

Another item I want to explore is the installation of an Air Scoop as there is none in the current system which has been installed for likely 40+ years. In general, it has been bullet proof until the compression tank started to leak.

The system has circulator pump and two zone valves. One zone is original to the house, built in 1924, and feeds larger black iron piping to radiators throughout the home with three supply and return branches. The second zone feeds baseboard heat for a kitchen and rear of house expansion completed in 2005. This zone has one supply and return in newer smaller copper piping.

Would it be advisable to install an Air Scoop for each zone as close to the boiler outlet (supply) where temps are highest or is one Air Scoop sufficient? As I understand, I would need to have the installation in a horizontal run where there is at least 18" of straight pipe before the Air Scoop.

Here are two photo for reference. Thanks.

Zman

A microbubble separator would eliminate the requirement for straight pipe. I verticle model might be a better fit for your system. https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Caleffi-551765A-Product Overview.pdf

WMno57

I recommend you replace the leaking tank with another plain steel air over water compression tank. That is what I did. You can read about it here:
https://forum.heatinghelp.com/discussion/181774/replacing-ceiling-mounted-thrush-compression-tank/p1
You mentioned in another discussion you may replace the boiler with a mod-con. If you do that in the future, I would have the contractor replace everything then.

• bladder tank
  
• microbubble thingy
  
• dirt mag
  
• primary secondary
  
• pump away
  
• etc
  

Start with all new stuff then, and have the contractor install it all. That way, he owns the installation.

hot_rod

I think you have just enough room to get a vertical air sep on top of the boiler before the first ZV connection.
There are no piping distance requirements with microbubble type separators.

Caleffi only goes to 1" on the vertical, bummer.

A Spiro combi would give you dirt, air and magnetic. It could be used on a mod con if you upgrade later.

I don't think I install a mod con to a compression tank system. If that is in the future go with the Extrol now.

WMno57

hot_rod said:

I don't think I install a mod con to a compression tank system.

Agree.

hot_rod said:

If that is in the future go with the Extrol now.

Disagree.
So you think it would make sense to install a new modcon on a 5 year old bladder tank. I don't. New boiler should get all new accessories at time of new boiler installation.
Maybe for you @hotrod it makes sense. You install everything yourself and can swap parts around at will. It's a different world for homeowners.
That leaking compression tank may pre-date the 1980 boiler. My old Thrush tank was 70 years old. Bladder tanks average lifespan is around 10 years. Really don't understand why the industry pushes bladder tanks so hard. Sure, on a new system they make sense. On an existing system, replace the failed part. Don't try to put lipstick on a pig.
One more thing @tdi. The payback period for that new mod-con is NEVER. You may eventually decide to keep that old WM.

leonz

Bob and I disagree on this,

Based on what I have for my system that has been operating flawlessly for 8 years now a larger wessels steel compression tank with an airtrol valve and sight glass gauge will provide you with greater benefit as it will provide more weight of water in the system and in my case eliminated crawling around on my double knee replacements which is frowned upon by the orthopedic surgeons and all I need to do at the start of every heating season is just turn the thermostat all the way up to drive any bubbles back into the steel compression tank.

There is no need for replacing anything as the airtrol and the steel compression tank with its water gauge
glass just hangs in between the ceiling joists silently doing its job. Mr. Holohan has one in his home and it has worked the same way quietly providing water pressure and air removal for decades.

The automatic air vents fail over time and leak and make a mess and you do not have that with a properly plumbed steel compression tank using either an Internal Air Separator or an air scoop connected to the Airtrol Valve.

I would definitely remove the automatic air valve and install a pipe plug in that elbow as it should not be used with a steel compression tank and will lead to flooding of the steel compression tank as the water feed needs to be shut off after the system is refilled.

I would still have my open to air expansion saddle tank hanging in my laundry room ceiling if I knew back then 41 years ago what I know now about heating with hot water and dry steam heating.

hot_rod

Where did the 5 years come from? Whats wrong with a 5 year old diaphragm tank? Average life span 10 years?

You are an exception, in the real world not many understand the concept, proper piping, air elimination, maintenance, draining and refilling, sizing, even proper support, of compression tanks. As we have witnessed over the past 20 years of posts here.

And your "never' comment is not realistic.

Why so angry today?

We all have choices. I think the HH community does a good job of laying out pros and cons on most any question.

WMno57

I'm not angry at you HotRod. I'm angry that as a consumer, every year my choices for quality equipment are less and less. Most of my options are now short lived junk. So I live in my own world where I drive 22 year old SUVs, heat with a 75 year old boiler, and maintain my reliable equipment with American made quality tools from 50 years ago.

hot_rod

WMno57 said:

I'm not angry at you HotRod. I'm angry that as a consumer, every year my choices for quality equipment are less and less. Most of my options are now short lived junk. So I live in my own world where I drive 22 year old SUVs, heat with a 75 year old boiler, and maintain my reliable equipment with American made quality tools from 50 years ago.

I get it, I get you We're good.

More bad news along the old technology lines in Canada today.

Jamie Hall

Yes -- but just think, soon you will be able to buy a Yugo electric car! And nothing else...

hot_rod

Jamie Hall said:

Yes -- but just think, soon you will be able to buy a Yugo electric car! And nothing else...

I doubt that.

Hertz is selling off the entire fleet of Teslas. Too expensive to repair, and insure. They crash more often than gas vehicles. Higher cash speeds with heavier vehicles gets expensive.

To fast, to quiet for the public to handle

EBEBRATT-Ed

Hertz is dumping the electrics and they are finding out the Teslas won't charge in the cold weather. When someone starts to realize the electric grid needs to be upgraded before going "all electric: then we can make some progress.

One of the electrical forums I go on they were posting about California mandating all electric houses. Some of the big houses out there they are talking about 600 & 800 amp services for a house...crazy.

And the POCO can't supply that.

I changed a service in a house for an old lady that lived in my town about 30 years ago.

She had a 30 amp 120 volt service in her house.

Changed that out to 100amp 240volt.

Jamie Hall

To replace Cedric with a heat pump (with, of course, resistance backup for nights like tonight is predicted to be) I'd need at least a 500 amp service. Not happening -- our local grid couldn't support it.

And with those bigger services, you almost need to start thinking three phase... won't that be fun.