Gravity Fed (Non Pressurised) Heating System

Yearning4Stormy

Folks,

I'm unsure of how a gravity-fed (non pressurised) heating system is plumbed - my own home is pressurised, so I get that you can turn off all the rads and have the water pumped around the distribution matrix in the attic (tis a bungalow).

Anyhow, a friend has a gravity fed system with a header tank in the attic. All the rads work except for the one in the front room (tepid is too generous).

Previously, another rad didn't work and he had the guy that installed the system (it's a 100 year old house) out to check it out. One of the rooms (upstairs) had a build up of, quote, "crap" in the Qualpex feeding the problem rad and a length of QP was replaced. This solved the original problem.

However, now another room has the same problem; all the rads in the house are piping hot except for the front room. To be honest, you could make it warmer by breathing heavily on it.

My pal is reticent to get the guy back again, so we've been busy coming up with mad plans to "flush" the system in the problem room. So far, this involves turning off all rads except the problem rad, connecting mains (albeit pumped well water) pressure somewhere (header tank feed?) and disconnecting the rad tails at the problem rad (with suitable drain-off mechanisms).

My concerns are (a) if it's plumbed like a pressurised system, the mains water will simply circulate around the distribution matrix and/or (b) that if there's a major blockage in the QP feeding that rad, nothing will happen: the mains water will treat the blockage as an "off" tap.

Any advice, folks? (And please excure my non-plumber terminology!)

JohnnieK

Sounds like you have a sludgy system and you would be as well to get it power flushed an sealed (providing there is no back boiler connected). If you dont want to spend the money on the power flush and go down the mains route you will have to blank the expansion pipe at the F&E tank and also the feed pipe. Flushing it with mains water will only temporarily solve the problem. It should be chemically treated, and then an inhibitor put into it to stop further corrosion.

Red Alert

By gravity I presume you mean an open-vented system, as opposed to gravity circulation through the system?

macnab

Just close off the 2 valves into the problem rad and remove it, bring it into the back garden and stick a garden hose onto one side. Flush until you are happy that its clear.

It may also be caused by a poorly balanced system.

Yearning4Stormy

Thanks for the replies, folks.

Red Alert wrote: »

By gravity I presume you mean an open-vented system, as opposed to gravity circulation through the system?

Sorry, RA, I assumed these were the same thing, no? "Open Vented" and "Gravity Circulation"? http://www.aquabrand.com/img/gravity.jpg

@JohnnieK, yeah, suspect it's a sludge problem (based on the experience with the blocked QP upstairs). Having it "professionally" flushed is not an option - money, money, money - but thanks for the tips on our original plan of using mains pressure water... even if it isn't a permanent solution.

Afaik, the well pump mechanism has had some additional inhibitors/etc added to it recently to reduce corrosion. I can't think of the term at the moment.

@macnad, that was the first thing we did and she's as clean as the day she left the factory!