Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Our first gravity fed hot water system

We just purchased a house that was built in 1939. It appears the original boiler for this home was coal fired and had been replaced in 1958 with a gas fired boiler. We found the original install packet, and manual for the boiler. To our surprise the 55 year old Stewart-Warner Winkler boiler is still working. I had no idea they could last that long. This is my first experience owning a home with hot water heat, and with a gravity fed system. I had a few questions about the system.

It appears that at one point the attic expansion tank was replaced with a green one that is above the boiler in the floor joist. We can see where the pipe was capped to where it used to run to the attic. I'm not sure if this was done in 1958 with the gas boiler. I am assuming that this is normal to no longer need the open system with the attic tank even though it is a gravity fed system.

The radiators on the first floor all get hot evenly through the entire radiator. The radiators on the second floor, only heat up on the bottom. Would this be due to air in the system, or could it be possibly due to corrosion?

We are impressed with how comfortable the heat is in this house. We would like to keep the system intact. We know it is a matter of time before the boiler needs replaced. We will cross that bridge when we get to it. We are trying to find a local professional to give it a look over and service it. We don't know who maintained it all these years. The previous owners have both passed. Someone had to take care of it for it to last all these years.

As usual the pipes are insulated with asbestos in the basement so we will have an abatement company in to remove it. Most of it is untouched and completely intact and a few small sections don't look good. Would it be necessary to re insulate the pipes in a gravity fed system?

We had considered replacing the system with forced air to give us AC in the summer months. However after researching and experiencing the incredibly even heat for our selves we would like to keep the hot water heat and possibly add a ductless mini split system for AC down the road, or just live with the window units.

Is there anything else we should take into consideration or be aware of with a gravity fed system? The very thorough article Dan wrote on gravity hot water heating was incredibly helpful.



  • kcopp
    kcopp Member Posts: 4,432
    Where are you....

    located? Gravity is nice.... is there still no circulator on there?
  • Voltztron
    Voltztron Member Posts: 3

    We are located in east central Indiana. Correct, it still does not have a circulator.
  • kcopp
    kcopp Member Posts: 4,432
    I would ...

    put some pressed fiberglass insulation back onto the piping. If they are un- insulated you will be losing heat to an area that it wasn't designed to go. Potentially it will slow response time. I am kind of surprised that in the Midwest where FHA is king that they have a gravity system..... Gravity as you know was a Canadian import.
  • MTC
    MTC Member Posts: 217
    Nice system

    Its great to see these old gravity systems still operational... half the time the "updating" of adding circulators and the like just ruins their simple beauty.

    Your system was changed from a compression tank to an expansion tank, it sounds like, or just replaced the old steel tank in the attic with a new one in the basement where its easier to get access to it. Either way, it performs the same function, essentially. The one thing that it might have changed was the old system of air removal...

    It sounds like your upstairs radiators have a substantial air pocket in the top of them, if they're only heating on the bottom. The expansion tank in the attic would have been a high point air relief, and likely would have kept the air from building up in the radiators. With it being at a low point now, it is less effective at removing air in a gravity system.

    However, you could also have an intentional amount of air in the radiators. This can be done for several reasons... to function as an artificial expansion tank - the air in the radiators will compress as the heat expands the water, much like a tank, or to reduce the effective EDR of the upstairs radiators, or both. Sometimes when you insulate a house, the upstairs, which was losing a ton of heat to the attic, starts to overheat. If the system seems even and balanced, I would probably leave the air in the radiators upstairs. Bleeding them may throw your system out of balance.

    I would definitely replace your pipe insulation with 1" molded fiberglass pipe insulation. Its not cheap, but worth the price in saved energy, and to maintain system design specs. 1" is the best value, going thicker doesn't add much except to the price tag.

    Def don't go forced air... you'll hate yourself if you do :) Minisplits can be a great cooling option. Not cheap up front, but very high efficiency is possible with them, keeping your running costs to a minimum. Look for the 20-26 SEER units for maximum long term cost savings. If you happen to have any trouble rooms with your heating system, the minisplits can have backup heating as well, can be a good option, but sounds like you don't need anything like that.
  • Voltztron
    Voltztron Member Posts: 3

    Thank you for the feedback. We had a guy who is familiar with older boiler systems come in and look at it. He recommended changing the thermocouple, and pressure relief valve since the age is not known. He showed me how to bleed the upstairs radiators. They warmed up nicely.

    We have a reputable HVAC contractor giving a quote for mini splits for AC.

    Where do I find molded fiberglass insulation for the pipes? I'm assuming I will need varying diameter as the pipes reduce in diameter down the run.
This discussion has been closed.