Question On Open Ended Expansion Tank Height

[hobbyheater]

My current Expansion tank is in the story above my boiler room; about 6 feet above the top of my storage tank. There is about 16 feet of 1/2 inch copper pipe between the storage and expansion tank and 12 feet of that run is almost level and has been there for the last 38 years with no apparent corrosion problems. The new boiler wants the expansion tank 98 inches above the top of the storage to prevent oxygenation. My question is this - does the 12 feet of almost level pipe reduce the need for more elevation between the expansion and storage?

 

[maple1]

Hmm, don't think I can answer your question with any confidence but would also like to know. I have rearranged my expansion over the years, now at sv90 and sv40 sized bladder tanks on the floor next to storage and a typical non-bladder tank up about 6' above storage that I valved off after putting in the sv40 tank. But I am borderline with having enough and have been thinking about opening that valve again or not. Used to have problems with one upstairs zone air locking sometimes. But think I have concluded that was due to low system pressure when cool because of pressure gauges that were inaccurate at lower pressures.

Edit: did you quiz Dean on it?

 

[mustash29]

My question is this - does the 12 feet of almost level pipe reduce the need for more elevation between the expansion and storage?

Nope. Feet of elevation will give you head (pressure). Feet of horizontal will not.

 

[hobbyheater]

Hmm, don't think I can answer your question with any confidence but would also like to know. I have rearranged my expansion over the years, now at sv90 and sv40 sized bladder tanks on the floor next to storage and a typical non-bladder tank up about 6' above storage that I valved off after putting in the sv40 tank. But I am borderline with having enough and have been thinking about opening that valve again or not. Used to have problems with one upstairs zone air locking sometimes. But think I have concluded that was due to low system pressure when cool because of pressure gauges that were inaccurate at lower pressures.

Edit: did you quiz Dean on it?

Dean suggested water treatment to eliminate any oxygen.

 

[hobbyheater]

My question is this - does the 12 feet of almost level pipe reduce the need for more elevation between the expansion and storage?

Nope. Feet of elevation will give you head (pressure). Feet of horizontal will not.

The question is not about head pressure which I understand but about oxygenation. Will the 12 feet of level pipe prevent it or does only elevation count?

 

[maple1]

Took a quick look at your manual. I was thinking you were talking about a typical bladder less 'old school' expansion tank. But you have a completely open expansion tank? Kind of like a head tank? Is there any way you can change it or add expansion of the closed type - say maybe even just a used tank water heater or 2? I started out with a 100 gallon lp tank but eventually converted to bladder tanks over time. I think my lp tank would have been ok if it was up high and not on the floor next to storage. Also noted the manual specs that height as above the highest point in the system. That would mean way up in the rafters in the attic for me.

Edit: looked again. It says ' distance', but doesn't say vertical or above. I guess that is the reason for the thread - it's a little open to interpretation.

 

[hobbyheater]

The expansion tank is a hot water tank in the woodshed above the boiler room. It is about 6 feet above the top of the storage tank and it does stay warm in the coldest weather so there has to be movement of the hotter lighter water through that level pipe. So does 2 extra feet of elevation mean that the lighter warmer water stops flowing to the expansion tank ?

 

[maple1]

Something I can't answer. But if things are expanding down below, it's going to push water into that tank. It has to have something to do with how far down the pipe oxygen/air can migrate, as things contract when cooling? I think, personally, I would run it like that, especially since you went so many years with no issues in the past.