Boiler T.P.R. valve blowing off

Our boiler emergency valve releases water every time the boiler runs. Pressure seems to start between 5-10 psi and rises to 30. The water leaks, pressure decreases and pattern starts over. We recently had the circulation pump replaced as the old one was not working and technitian believed that would solve the TP valve problem. It did not but the valve seems to be in working order. After reading a lot on here we have determined we need to drain the expansion tank (although it sounds hollow and is cold to touch). The trouble is that there does not seem to be a drain valve on the tank.

Here are some notes on our system:
Our home was built in 1900 and we heat it with the original coal boiler that was at some point converted to gas. No idea how old the expansion tank is. We have lived here 2 years and had the systemed "serviced" last year but all the guy did was bleed the registers. Not sure how long the pressure thing has been happening, seems like we've emptied a bucket every few days in the winter since we moved in (didn't realize it was a danger until researching it a bit).

Sorry for the long post, I'll try to add some pics.

 

If the expansion tank is a bladder type tank it probably has either lost it's air charge or the bladder is bad (or both). Here's a link on how to check/service it. http://www.doityourself.com/forum/bo...-new-post.html

If it is a conventional type with a drain valve, it probably needs to be drained.

 

It's def not the bladder type. It's a horizontal steel tube attached to rafters in basement. Looks pretty old. The only pipe that going in runs to the circulating pump and on through boiler. No drain at all.
Any tips on posting pics?

 

Welcome to the forums.

Here's some tips for posting pics.... http://www.doityourself.com/forum/el...rt-images.html

 

Thanks for the pic tips trying to do this from my phone so hope it works!
The 1st pic is of the expansion tank (sorry it's upside down). The pipe coming out is the only access we can seem to find on there. It travels down to the circulating pump.



The next pic is the boiler...keeping this home warm for 100+ years! You can see the expansion tank and pipe I speak of on the left.



Thanks in advance for any advice!

 

The expansion tank is evidently waterlogged - without an air cushion, the pressure will be too high.

Look at the second pix. On the end of the tank, are those threaded connection points that are plugged? If so, the lower one should have a boiler drain valve installed.

Also, in the same pix, do I see an air eliminator device? If so, it needs to be removed - it will deplete the air in the exp tank.

You will need to cool down the system and depressurize it to work on the system

 

From what I'm seeing, it doesn't look like the pipe from the tank goes to the circulator. Can you get a picture from the left side of the boiler looking across the back so I can see the piping?

I'm wondering if that is actually the expansion tank. Unusual to see one galvanized & to see what appears to be the name John Wood. I think it is an old range boiler for domestic hot water. I'd bet those two plugged tappings were the domestic & plugged when the water heater was installed.

 

Thanks for the feedback!
I'll work on the pic Grady. As far as the air eliminator device I'm not sure what you are referring to Gilmorrie.

 

The green 'can' on top of the pipe, can be seen in both photos.

 

Some additional minor points. A TPR, rated in Btu/hr, is typically used for fired domestic water heaters. Hot-water boilers usually just have a pressure relief valve, typically with a 30 psi setpoint. I doubt that yours is a TPR valve, but check to be sure.

Even though your house is 100 years old, your boiler isn't that old. I see what appears to be strap-on aquastat on the supply pipe from the boiler. That should be OK for a backup hi temp safety cutoff if it has a manual reset. For normal control prurposes, it is preferred to have an aquastat with its sensor bulb installed into a thrmowell.

 

Crazy weekend, thanks again for all of the input.

Gilmorrie : I believe you are right about it just being a pressure relief valve. The gauge is at on the boiler side of the "auto/manual fill" lever and that is what climbs to 30, but the relief valve is on a pipe coming out the back of the boiler and that is what drips. The home inspector told us this was the original coal boiler converted to gas but I guess you are right that it was not necessarily original to the house. There are round covers in each chimney in different rooms I'm assuming were for pot-bellied stoves for heat early on. Also, there is a 2nd auqastat control on a pipe directly on top of the boiler. They are both set at 160...is this OK?

As far as the air eliminator device: how does this work? Do I use it to bleed the system instead of register by register? Will the expansion tank work with it?

Here is some good news, although you might all have reasons why we shoildnt have done it:NO NO NO:we did get the expansion tank drained (assuming it is actually the expansion tank). It was FULL of water! We had to do it by draining the entire system though, so will def be figuring out how to install a drain valve on there by next year. It was a pretty lengthy process but we are back up and running and the pressure has been sitting at 10 ever since. The house is warm so that's good! We know we need to get the pressure up to 12 psi. We need to get a new valve for the kitchen register as it appears to have an ever-so-slight leak. Maybe that will bump it up. We'll see.
I'd love any more feedback. Thanks!

 

You have to remove the air eliminator device and plug the connection with a threaded plug. Otherwise, the over-pressure problem will happen again.

My previous comments about the strap-on aquastats still apply.

 

How do you know that you got the water out of the tank by draining the system?

Without some other opening on the tank itself, a vacuum would have formed inside the tank and held the water in, just like when you put a finger over a drinking straw and lift the straw out of the drink.

Did you remove one of the plugs on the end of the tank?

 

So any ideas why the air eliminator device is there if it will cause the pressure to rise? I'll look into the aquastat. As far as daring the tank goes, we could hear the water in the tank, it sounded like a very loud, metal water cooler. I'm assuming air got in there as the system drained and forced the water out, we didn't open any thing but the main drain valve.

 

It won't directly cause the pressure to rise. It will vent the air from the system which in time will cause the air in the expansion tank to disappear, which will ultimately cause a pressure problem.

Ignorant persons install air vents for various reasons without knowing why or why not they should or shouldn't be.

 

If you're comfortable with that assumption and the pressure is now OK, they it's all good...