2 questions about re-attaching cast iron radiator to an old radiant heat system.

Reply

  #1  
Old 10-17-11, 10:31 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
2 questions about re-attaching cast iron radiator to an old radiant heat system.

After renovating the bathroom in a house with an old gas-fired boiler, I need to put the cast iron radiator back into place, but I have a couple of questions:

1. I'm not sure how tight to make the fittings that connect the radiator to the intake/outtake pipes.

For example, I can hand tighten the intake fitting 1/4 turn past the radiator coupling before it gets very tight. I'm concerned about using a pipe wrench to tighten it the final 3/4 turn to line up with the radiator coupling again. However, if I leave it as is the fitting will be somewhat snug but I can move the fitting by hand.

2. I need advice on how to recharge the system.

This old boiler does not have a pump, and the water moves through the system by convection and gravity feed. Before removing that heavy radiator from the bathroom, I emptied the system by attaching a garden hose to the drain spigot on the boiler. When I add water to charge the system up again, do I need to bleed air from all the radiators throughout the house using the small valves located at the top of the radiators? What's the best approach/order to do this, and what happens if some of the radiators don't have a functioning valve (ie. the knob is missing and what is there doesn't look like it would turn)?

I need to get this done asap as the weather is starting to get COLD up here!! Thanks for any help!
 
Sponsored Links
  #2  
Old 10-17-11, 11:14 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 18,012
Received 39 Votes on 34 Posts
Hi,

ell make sure the surfaces of the couplings are clean. You may want to use some pipe dope on the threads and lightly on the mating surface. But after you clean them up good.

I would not go hog wild tightening them. Use a smaller wrench, like a 10" and snug it. When you run the system and you see a leak you can snug some more.

This way you would break/ crack the nut. If so then youll have issues. If you ever tried to get the spud out of the radiator to replace it you will know what I mean. They dont go easy.

For air I would start at the farthest, and upper floors. That will get the water fill initially in the mains, but then you will need to go around to each rad and bleed.

If the bleeders dont work, it best to change them all know while the system is drained. It would be silly not to.

Mike NJ
 
  #3  
Old 10-18-11, 09:25 AM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
Thanks Mike, I will definitely purchase some pipe dope and use that instead of teflon. As for tightening, I might not have explained myself that well. I'm not worried about tightening the coupling (that's attached to radiator) to the fitting, it's twisting the fitting onto the threaded straight pipe coming out of the floor where I'm concerned. When I tighten it to a point that it's in line with the radiator coupling I don't think it's quite tight enough, but I don't want to force it around another turn for fear of damaging that joint, but maybe I don't have a choice? Roughly how tight should that joint be? Like I said, as it is now I can move it by hand, but once I hook it up to the radiator coupling I won't be able to adjust that joint anymore.

I would love to replace all the bleeder valves, but am dealing with an old system and figured replacement parts would be difficult to obtain. I've (hopefully) attached a picture of what I'm dealing with, but maybe there's a standard sized bleeder valve and I just need to find some online?

Again, the help is much appreciated!

 
  #4  
Old 10-18-11, 07:17 PM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
You should have about 8 threads of the pipe into the fitting. Use no more than 2-3 layers of teflon tape on the threads and keep it off the first thread or two. I assume that these pipes are at least 1" in diameter. You may even want to consider a very light coating of dope on top of the teflon. I was having trouble last weekend with some threaded fitting myself and resorted to the light coating of dope. The idea of the teflon tape and pipe dope is to lubricate the threads so you can get them to mate more easily. It is the mating of metal against metal that seals the joint.

You should be able to get air vents (bleeder valves) at Home Depot.
 
  #5  
Old 10-19-11, 09:31 AM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I used pipe dope on the joints which I think really helped. I used a small pipe wrench as suggested and the dope made it easier to turn the fittings so the joints are nice and snug now. I will try Home Depot for the bleeder valves, just didn't think they would stock something that would fit my old rads - hope I'm pleasantly surprised. Thanks for all the help and suggestions, hope to have a warm house again by this evening!
 
  #6  
Old 10-19-11, 03:37 PM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
At my HD, they have a small section for boiler related items. That's where I saw the vents. If you live in an area where hydronic heating and old homes are abundant, I would think they would have them as well. If not, hit up your local plumbing supply. I believe that go into an 1/8" tapping. I have never changed one myself but I would be real careful putting the new one in. A tapping that small would be easy to over tighten.
 
  #7  
Old 10-20-11, 10:27 AM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I checked all the big box guys yesterday (Lowes, HD and Rona) and the best I could do was a small brass plug, but did manage to find some air valves at a local plumbing wholesaler today. It is 1/8" tapping so I will heed your advice and be careful not to overtighten. Should I use teflon on the threads or no need?
 
  #8  
Old 10-20-11, 10:33 AM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 18,012
Received 39 Votes on 34 Posts
Should I use teflon on the threads or no need?
Yes but only like 1 or 2 wraps. Too much and you may cross thread. Its hard to thread with alot of tape. Also dont tape the first couple of threads. Those threads are small.

Good thing is to clean the threads up with a small wire brush.

Mike NJ
 
  #9  
Old 10-21-11, 07:40 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I've replaced all the air valves using a little teflon tape as you suggested and am ready to refill the system.

Originally Posted by lawrosa View Post
For air I would start at the farthest, and upper floors. That will get the water fill initially in the mains, but then you will need to go around to each rad and bleed.
Just to confirm, as I have two different lines leaving and returning to the boiler, I should open each of the bleeders at the end of these two lines while filling the system. Once water begins to leave the valves, close them off and then begin to bleed the rads back toward the boiler.

Do I need to do an additional air bleed once the water has been heated?
 
  #10  
Old 10-22-11, 05:56 AM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
If you are doing this alone, leave the bleeders closed. When I recently refilled my system, I brought the pressure up to 25 psi and then shut off the fast fill. Then I went upstairs to bleed air from the radiators. When the air coming out slowed down, I went back down and put more pressure in the system. Filling to 25 psi helps bleed the air faster. At the end if you have more than 12 psi, just empty some of the water out of the boiler to bring the pressure down. You may have some air collect in the rads again after it has run for awhile. It wouldn't hurt to go around and bleed them after a few weeks. Obviously if any radiator is noticeably cold at the top, it's full of air.

A second person definitely makes this job easier. One person can go around bleeding while the other person stays in the basement and maintains pressure.
 
  #11  
Old 10-22-11, 08:34 AM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I am doing this alone but thankfully a small bungalow so not too many stairs. Approximately how long did it take you to refill your system? I'm a bit concerned that when I had an initial go at this last night the pressure gauge always seemed to read zero... could there be a possible issue with the pressure reducing valve? Going to give it another go this morning and will do a better job of watching the gauge.
 
  #12  
Old 10-22-11, 09:08 AM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
Is there a fast fill lever on your pressure reducing valve? If you don't have one, it will take awhile to fill the system. It also depends on how large your pipes are. When I refilled my 1st floor zone, that took several minutes to bring up to pressure. That zone was designed for a gravity system so the pipes are large. You should be able to hear the water flowing through the pipes.
 
  #13  
Old 10-22-11, 01:10 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I think I was bleeding off all the pressure before I was checking the gauge. The pipes are quite large but I managed to get the system filled and all the air bled off. I left the pressure at 12 psi cold, but what kind of pressure should I be seeing while it's heating up again? I think it was hitting 40 psi.
 
  #14  
Old 10-22-11, 01:15 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
There is a very good possibility that your pressure gauge is messed... they are notoriously inaccurate! Before troubleshooting any further, you need to verify the accuracy of your gauge.

The pressure relief valve on your boiler ( almost always 30 PSI for residential systems ) would have opened long before you hit 40.

You may have an issue with your expansion tank if the pressure is increasing too high too fast.
 
  #15  
Old 10-22-11, 01:27 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
This is a very old system so the gauge could be inaccurate as you say. Can the gauge be swapped out without having to drain the system?

Having said that, during the heating cycle I had noticed that the boiler had stopped heating and the pressure was down to 30 psi. I don't believe this system has an expansion tank. From what i've read they usually have a little viewing window to see the water level in the tank?

It's been a few hours now, and the pressure is sitting at 30 psi. Faulty gauge or result of relief valve (which is rated for 30 psi) doing its job? Should I leave it for now, or try to bleed some of the pressure off?
 

Last edited by rudeboy; 10-22-11 at 02:53 PM.
  #16  
Old 10-22-11, 05:47 PM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
You would know if the relief valve blew. Water would be all over the floor. You can rig up a test gauge that attaches to your boiler drain. I'm sure Trooper will be kind enough to post his instructions yet again on how to do that. You can use that until you feel up to draining your system again to replace the one on the boiler.
 
  #17  
Old 10-23-11, 08:08 AM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
You would know if the relief valve blew. Water would be all over the floor.
Okay, didn't have that happen. There is an additional 1/2" line leaving the relief valve (so 1 in and 2 out) that disappears into the wall, and figured that might be where the water would exit if the relief valve opened up.

So it initially peaked at 40, ran at around 30 for the extended heating cycle, dipped to 22 for awhile and once the house was heated up again and the boiler was dormant for an extended period of time, the gauge read 8 psi. A test gauge would be good, because I don't trust those readings now at all.
 
  #18  
Old 10-23-11, 09:26 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
For about $10 or so, you can purchase one of these:



Problem with this is that the 300 PSI gauge gives very poor resolution at the low pressure ranges.

You could purchase an additional pressure gauge at a real plumbing store, or perhaps a pool supply store and replace the one that came with it... and just use the fitting. Look for a 0-30 or 0-50 PSI gauge.

Or, you could buy the fitting and gauge separate and make your own.

I use one that I made with bits from my junque boxe:



Screw this onto a boiler drain and open the drain valve to read the pressure.
 
  #19  
Old 10-23-11, 09:30 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Rude, it sounds like your system may be ummmm... less than 'up to code'... 1/2" pipe from a relief valve going to an unknown location somewhere on the other side of a wall is kinda 'flaky'... I'm betting, guessing that your relief valve may not be an ASME rated part... and 1/2" pipe isn't large enough.

Can you take pictures? Set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload your pics there. Come back here and place a link to your PUBLIC album for us to view.
 
  #20  
Old 10-24-11, 08:30 AM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I appreciate the instructions on how to assemble a temporary pressure gauge, will do that this afternoon. As for the relief valve I'll take a couple of pics today and post them later for you to take a look at. Thanks.
 
  #21  
Old 10-24-11, 02:47 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
Upon closer inspection, I think the pipe goes from relief valve to floor drain, and just travels inside of the wall framing for a bit. And it looks like 1" pipe (at least 3/4") and not 1/2". Here's a couple of pics, let me know what you think. Thanks.






 
  #22  
Old 10-24-11, 03:51 PM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
That is not your pressure relief valve. That would be your pressure reducing valve/auto fill valve. That auto fills your system to a preset pressure and does not allow the city's pressure to make it higher.
 
  #23  
Old 10-24-11, 04:04 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I see. I saw relief valve (30 lbs) written on there and figured that was what it was. I'll take another look.
 
  #24  
Old 10-24-11, 04:24 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I believe that's a combination unit... but I can't recall seeing one like that... usually the 'combos' are two separate devices.

Your pic is rather small, but I see two 'settings', one 12 PSI, the other 30 PSI.

In any case though, that wouldn't be up to modern codes. All modern boilers have a relief valve mounted right on the boiler itself, and it is rated to pass the full flow of a catastrophic failure. Your valve might not be able to do that. That's why they changed the codes.

Most jurisdictions now require a backflow preventer in addition... like this:


image courtesy ccallis.com

This prevents boiler water from getting into the domestic supply.

Is there another relief valve on the boiler itself?
 

Last edited by NJT; 11-18-11 at 05:45 PM.
  #25  
Old 10-24-11, 10:28 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I checked the boiler for an on-board relief valve but couldn't find one (I think the boiler is original to the house which was built in 1925)...definitely not up to code. The only other thing of note is a 2" copper pipe tied into one of the outlet lines near the boiler itself, but I'm not sure what it does or where it goes (I know I know...more sketchy plumbing).

 
  #26  
Old 10-27-11, 10:21 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
I managed to put together a temporary pressure gauge hooked up to the drain valve, and it works really well.



Thanks for all the great suggestions and help!!
 
  #27  
Old 10-28-11, 05:27 PM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
Oh wow. So I guess you didn't have hose threads on your drain.
 
  #28  
Old 10-28-11, 05:43 PM
Member
Thread Starter
Join Date: Oct 2008
Location: Great White North
Posts: 218
Received 1 Vote on 1 Post
Ha! No, just a 3/4" female thread...but this works too![HR][/HR]
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: