Hot Water Heating System Pressure Too High

Your expansion tank may very well have failed. The only way to check it is to remove it and check the air pressure, if the tank is heavy, your expansion tank bladder has failed.

One thing you need to keep in mind is you need to keep the water feed valve off after the boiler is filled and the pressure is correct after you bleed the system.

You can always check for a tankless coil leak by turning off the feed valve to the tank less coil removing the connection to the coil and opening the water feed valve for the boiler to verify it is not leaking.

If the bladder tank has not ruptured and the domestic hot water coil is not leaking turning the heat up on you thermostats and leaving it for a few hours will drive all the air out of the system as long as the air vents are not damaged and leaking- I hate those things. As long as you are into this repair this far, I would buy 2 new vents and the quarter inch pipe, pipe couplers and a ball valve for each one to allow you to change them without draining the boiler when they start leaking.

You will not go wrong if you replace the existing pressure gauge with an American made triple gauge from Marsh Instruments. They offer a 3 year warranty for workmanship from what I remember of my purchase of my 4 inch square triple gauge and they also offer a repair and recalibration service if needed.

If the expansion tank has failed installing the next larger size expansion tank will only help you as it will provide you with more room for expansion and provide you with a larger point of no pressure change since you are pumping into the boiler.

Perhaps now it would be best to send the boiler to the "great boiler hunting ground" before the heating season comes based on what you have mentioned previously?

The way my coal stoker boiler was installed by the clown car plumbers I hired took 3 days longer than it should have and cost much more than it should have because of the digital boiler controls that nearly blew up my house with the first unit with weeks of no central heat in January of 2015 and the second digital unit failed with flying colors and 5 months worth of bad words as well.

You lose faith in a hydrolevel digital control system while you are standing there watching the boiler temperature rise and the computer in the hydrolevel 3250+ system turns off the low water cut off switch!!!!!!!!!!!!!!!!!!!!

After that I purchased a honeywell L8124L mechanical triple aquastat, a Marsh Instruments 4 square inch triple gauge and a McDonnel & Miller RB-122-E immersed low water cut off switch to replace all the chinese made junk and round pressure gauge.

I will tell you that when I had a 15 gallon Bell & Gossett steel compression tank installed with the coal stoker for air management it solved my air problem with 225 feet of 3/4 inch fin tube baseboard(which I hate) by simply turning up the thermostat.

I used 3 of Mr. Holohans books in designing my new boiler system, they are CLASSIC HYDRONICS, PUMPING AWAY and HOW COME and they were a blessing to me as I told Mr. Holohan.

No more crawling around on artificial knees ever as I have 10 plus gallons of water mass above the boiler to create the point of pressure change to flood the suction of the B&G NRF 25 circulator set at speed one which is 12 gallons per minute that is not properly regulated due to the 1 inch tee that the hot water is pumped into for my 54 gallon system.

I used the diagram Mr. Holohan created for a steel compression tank in his pump module drawing and it has worked flawlessly except when I had a screaming vacuum leak which I traced to the packing gland nuts for my water gauge at the end of my steel compression tank. A quarter of a turn on the packing land nuts solved that issue.

A steel compression tank eliminated the bladder tank, air scoop and automatic air vents in my old system.

When assembling the pump module you can use an air scoop to feed the airtrol valve under the steel compression tank but using an Internal Air Separator to direct the air bubbles to the airtrol valve is simpler as the Internal Air Separator had a cast in place baffle the directs the air bubbles into the pipe that comes out of the top of the Internal Air Separator which directs the air bubbles to the airtrol valve threaded into the base of the steel compression tank. The air bubbles in the hot water pass through the airtrol valves hopt water casting to the warm water via the copper pipe in the airtrol valve and then into the steel compression tank and dissolve in the air blanket. The cooler water in the steel compression tank simply drops through the Airtrol valve via the cold water side of the airtrol casting and back into the hot water flow.

with my system my water feed valve is shut off completely as I do not need to add water to my system and no water enters the system through back flow preventer as the system is full of water.

Yes, your bladder tank is bad and needs to be replaced.

The bladder disc has ruptured and can no longer work as your systems point of no pressure change as it is water logged.

It would be a good management decision to change out the automatic air vents with new ones as long as you have come this far.

If you have a paint pen it would be a good idea to paint the date you replaced them on the air vents and the bladder tank so you have a future reference.

Hello and good afternoon BrooklynMike,

If the fill valve is set with 12 pounds pressure that will work, all you need to do is turn your thermostat all the way up to heat the water in the boiler and drive out the air bubbles. After a couple of hours all the microbubbles should have passed through the new automatic air vents and then you can shut the fill valve off.