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Tom
Tom, HVAC Technician
Category: HVAC
Satisfied Customers: 770
Experience:  16+yrs HVAC/R service. Residential Commerical Industrial
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I have a hot water heater gas furnace with radiators that heat

Resolved Question:

I have a hot water heater gas furnace with radiators that heat the house. I was told that my boiler is over tilling and need a new reducing valve. How much time does this take to fix and how much should I pay? Can a regular plumber do the job or do I need one that specializes in Heating and HVAC Plumbing - can you recommend what who should do the job and time and cost to complete the job.

Also the past few winters we have had high gas bills is this related to the valve also noting that the top floor radiator in the front rooms are not heating - is it normal to drain and fill the radiator system every year - what is the function of the reducing valve.
Submitted: 3 years ago.
Category: HVAC
Expert:  Tom replied 3 years ago.

Tom :

Hi,,,,quite a few questions here....I'll try to address them as we go here,,but first I need to know a couple of things. Who told you it's overfilling and what is happening that made them think that?

Customer:

I was told by the Service Technician / company that installed the Gas Furnace and Hooked up all the plumbing some time ago. If I am not mistaken the reason why we need to change the reducing valve is because it is not working and not recirculating the water.

Tom :

Ok....

Tom :

Lets start at the beginning..

Customer:

Each year we have to call them out to fill our system to get all the rooms heating

Customer:

ok

Tom :

The fill valve's purpose is to reduce city water pressure (or well pump) to 12 psi to supply the boiler system

Tom :

City water will run 60 - 80 psi (pounds per square inch)

Tom :

The pressure relief valve on your system is set to relieve at 30 psi.

Tom :

Therefore we have to knock down the entering water pressure or your relief valve would always be dumping water.

Tom :

If the fill valve was indeed over filling....your system would over pressurize and the relief would pop and you'd have water on the floor. Does the relief valve ever leak?

Customer:

yes that that has been the case a few times

Tom :

Ok..is it resolved by valving off the inlet water supply?

Customer:

don't think it is the valve that leaks but it comes from the hot water heater

Tom :

correct...there is a relief valve on the boiler that probably has a pipe extending to the floor that will leak if system pressure goes over 30 psi.

Customer:

ok

Customer:

but there is a overflow tank i believe

Tom :

boiler relief valve

Tom :

Boiler service can get a little complicated...everything has to work as a system...

Tom :

The tank you are referring to is the expansion tank....

Customer:

it's a bell valve without a lever I think not like the one shown

Tom :

Ok......lets clairfy which valve we're talking about..

Customer:

ok - yes expansion tank

Tom :

The bell valve...you're referring to the 'fill valve' that is in the cold water supply pipe correct?

Tom :

typical fill valve

Customer:

it is on the line entering the furnace i think

Customer:

i think that is it - that is what they tell me needs to be changed because it is not opening and closing as it should

Tom :

Ok....so...again..that valve's entire purpose is to supply water to the boiler.....at a reduced pressure...I'm not saying "never" ...but seldom do they overfill...they often stick shut...but seldom overfill.....so I'm going to try and outline a few things that need to be checked. ...Hopefully that will give you some info to question them on.

Tom :

how long have you owned the house with the boiler system/

Tom :

/

Customer:

It was installed October 1991 brand new

Tom :

ok...I don't know your knowledge level..so please bear with me..

Tom :

Are you familiar with the purpose of the expansion tank

Customer:

ok

Customer:

no

Tom :

Ok...as I said ..this all has to work together and one component not working makes an unhappy system..! I'll do my best to explain.

Customer:

is that for water going back to the hot water heater

Tom :

no...is your hot water heated by the boiler as well as supplying heat for the house?

Customer:

the hot water tank has it's own pilot

Tom :

Ok..some boilers heat the domestic water..just asking...ok here goes..I'll type fast as I can

Customer:

i think the furnace is strictly for the radiator system heating the house

Customer:

hot water is independant

Tom :

we like to run the boiler pressure at 12 psi COLD......as the water heats the pressure in your boiler will increase...to around 18 -22 psi HOT on a properly working system

Tom :

Ok

Tom :

The fill valve is normally set to supply the city pressure at 12 psi and then it should shut off.

Customer:

ok

Tom :

Now...the expansion tank is in the system to absorb pressure from the water expanding in the pipes and boiler.....as it heats....the water expands...and it has to go somewhere ... the expansion tank provides an 'air cushion' for the expansion....

Tom :

IF the tank is bad or water logged (i'll explain in a minute)..your system will overpressurize and pop the relief valve and you get water on the floor......

Tom :

Then the fill valve will take over and add water back to the system..and it starts all over again.

Customer:

ok

Tom :

does your expansion tank look anything like this??

Tom :

Or is it nailed up in the floor joists?

Customer:

Long and narrow mounted above the furnace - similar

Tom :

Ok..mounted horizontal up in the ceiling?

Tom :

typical install of horizontal tank with Airtrol fitting

Customer:

not in the ceiling but strapped to structure above the furnace

Customer:

that looks like it

Customer:

yes

Tom :

Ok...soooo...the expansion tank should be about 1/3 to 1/2 full of water and the rest air.....

Tom :

IF the tank has become waterlogged over the years... it simply acts like another piece of pipe in the system because the air cushion is gone....

Tom :

When the water heats sufficiently it expands..has nowhere to go and pops the relief valve.

Customer:

ok

Tom :

If i were to service your system...I would have to look at everything...based on what you're telling me...I would like to work on the system cold at first.

Tom :

Make sure the fill valve fills the system to 12 psi and shuts off.....you can usually here the fill valve pinch down and whistle a little as it tapers off.

Tom :

I would probably valve off the expansion tank...there is usually a valve inline to it...and drain it completely...

Customer:

yest that has been done before

Tom :

then open the valve and let the fill valve add water to 12 psi. By emptying the tank and letting it refill through the fill valve it should re-establish the air cushion if it was lost.

Tom :

Ok...that should take care of the pressure issue...IF the fill valve is not overfilling. If pressure continues to rise over 12 psi with the boiler cold...and boiler pump turned off...then you know the valve is either bad OR someone has turned the adjusting screw on top to too high of a pressure.

Tom :

There is a screw adjustment on top that guys will sometimes turn in to make it fill faster...it needs to be backed out so that it stops at 12 psi.

Tom :

If that is still not a problem then you probably need a fill valve.

Customer:

ok

Tom :

Now....as for the radiator not heating...you do run a circulator pump correct?

Customer:

i do not know

Customer:

I was only told the fill valve is not working

Tom :

anything like or similar to this mounted near the boiler with pipes and wires attached?

Customer:

I have never seen it and it has never been pointed out by the service tech - is this standard for the type of system I have?

Tom :

yes..unless you have a very old 'gravity' system which would have fairly large pipes on the boiler to allow gravity circulation of the hot water

Customer:

yes we do still have the large pipes on the basement level only coming down and going to the boiler but that was never changed only a new furnace has been installed

Customer:

would like to get rid of those bulky pipes

Tom :

Is the expansion tank in the basement or attic?

Customer:

it was originally in the attic but when the new furnace was installed it was taken out and a expansion tank was installed in the basement above the new furnace

Tom :

Ok...then it should have a pump..

Tom :

It was probably a gravity system converted to a pressurized 'closed' system.

Customer:

yes

Tom :

Do you ever hear water rushing through the pipes when the heat is on?

Tom :

or gurgling or trickling or whatever you want to call it?

Customer:

no but the two large pipes going to the furnace do get hot just like the radiator pipes

Tom :

Ok good..

Tom :

you should not hear water in the pipes at all....

Tom :

Do you have old cast iron radiators?

Customer:

yes

Tom :

So..if one upstairs is not getting hot...either it is air locked.....or the bottom of it could be full of 'mud' not allowing water to circulate.

Customer:

only problem is with the front of the house not completely filling which does not effectively heat the rooms

Tom :

Does each radiator have a bleeder on it?

Customer:

yes - they have been bled and have to be refilled manually to get the rooms heated

Customer:

they say this is because of the fill valve is that correct

Customer:

or bell valve reducer

Tom :

possibly....but that conflicts a little with the orignial conversation of it overfilling

Tom :

Are you at home now?

Customer:

yes

Tom :

I'm really curious if there is a pump on the return side of your boiler..if so pressurizing it should be no problem.

Tom :

You shouldn't have to manually fill radiators

Tom :

sorry 2 thoughts going at once

Customer:

manually meaning that they need to refill the system

Tom :

oh...you don't actually pour water in them?

Tom :

not sure what you meant by manually refilling the system I guess...Sorry

Customer:

that is what i am trying to resolve

Customer:

refilling the system each winter season because the fill valve is not working

Customer:

is this the problem

Customer:

like to know how long the job should take and how much cost wise I should pay to repair - I am located in Washington DC

Tom :

Could be.....if the system need refilling.....and nothing is apparently leaking...I'm thinking you may have some pinholes in your expansion tank...that would explain a couple of things...the need to add water and if there are some pinholes....it would allow the air cushion to escape the expansion tank which leads to the relief valve popping now and then

Customer:

thanks for looking into this

Tom :

My company charges about $90/hr....should be able to change a valve in an hour and a half or so provided it is able to be isolated from the boiler. If there is not shutoff between the valve and boiler the system will have to be drained which is going to get you into more time...probably 2 1/2 to 3 hrs pretty quickly.

Tom :

The valve itself will run around 50 - 75 dollars

Customer:

would you confirm their diagnosis

Customer:

or based on our discussion this is the problem or other things too

Tom :

The fill valve can be tricky...based on our discussion I would try filling and listen carefully and watch the pressure gauge on the boiler to see if it shuts off. Then I would check the expansion tank to see if it needs drained and also if there is an air vent on the boiler and if so ..is it working properly. As I mentioned...all of these things have to work properly in unison or you'll have problems simlilar to what you're describing.

Tom :

I wouldn't automatically assume a new fill valve is going to fix the problem.

Customer:

ok

Tom :

And to answer one of your last questions...you should not have to drain and fill the system every year. If everything is tight and not leaking...you shouldn't have to touch the water side for several years once it's all running properly.

Customer:

yes that is how i remember it should be

Tom :

I would probably emphasize that they check 3 things...Fill valve,,,air vent...expansion tank

Customer:

the system is closed and right now the only problem is the upper two room radiators are not getting water in the radiators

Tom :

That could be a fill valve issue...or it could be they are air locked...and need the air bled off....if you open the bleeders and get nothing...I'm supposing the fill valve is not providing enough water pressure.

Customer:

also i noticed my gas bill to be high in the winter months does this have anything to do with the system

Customer:

not working 100%

Tom :

Well..if you're not getting the radiators all warm..you're probalby running it longer than usual to try and get some heat. Also..in mild weather you could turn the water temp down on the boiler ...you don't need it as hot on a 30 -40 degree day as you do on a -10 day.

Customer:

ok

Tom :

I hope that answered some of your questions...anything else i can answer for you?

Customer:

thanks you

Tom, HVAC Technician
Category: HVAC
Satisfied Customers: 770
Experience: 16+yrs HVAC/R service. Residential Commerical Industrial
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