Fill Valve Open or Closed?

hot_rod

Yes it is a discussion worth having.

I suspect that language to valve them off is written by attorneys, not the contractors that get up in the middle of the night to go on the no heat call :0

I would also say modern mod cons, all modern boilers, are less apt to "glow red" compared to the older cast iron beasts.
Liability concerns has upped the number and redundancy of safety devices. I remember a time when some boiler gas valves didn't even have safety pilots! My dads truck with a shelf full of Basco add on safeties. Equipment has become safer and safer since those days.

Heck the legal boys even managed to get the lead out!

Also the use of plastic and rubber and miles of radiant tube changed the way system hold and drop pressure.
I have a few early rubber tube system I babysit. They hold a 60 psi air test for weeks, but need a quart of fluid added to them every heating season??

Steel and copper joints seem to hold pressure and last a lifetime, not so much with rubber and plastics, often due to installation errors, bad crimps, mismatched compression fitting brands, hose clamp failure, etc.

Jean-David Beyer

Has this article been found to be incorrect?

https://heatinghelp.com/systems-help-center/should-fill-valves-be-left-open-or-closed/

DanHolohan

No.

icesailor

Another conundrum. It can be off. Until it needs to be on, and sometimes, it should have been left off.

Whatever route you choose, will be right mostly or wrong mostly.

I once went to a house that I was called to turn on the water and heat for the Latino cleaners. Who went early, before they were supposed to go by the owners. They were good pay so they treated them first ahead of the slow payers. I get a call that there is no hot water. I get there, the cleaning girls were gone. The boiler was ON and the circulators were running. There was no pressure in the boiler and all the drains were open. The well pump was off. The house was as totally drained as it was in the Fall when someone (not myself) had drained it.

I knew enough to not turn on the water to the house or fill the heating system. Something about cold water into a hot cast iron boiler.

All was good though. The old boiler was something the owner had salvaged from a house he tore down, so he got a new one.

All was then good.

That hot water switch. You've got to be really careful of it. Why I always take the Firomatic fuse out of the loop when I drain systems. If they can't read and understand English, and it becomes too complicated, they might give up. Unless they have some smart boyfriend who knows a lot. Like flip the switch and the burner starts. All is well.

Sometimes.

hot_rod

The I&O manuals I found online for these common fill valves or combos.
Watts 1157,
Taco 329 and 3350,
Caleffi 553 and 535,
Honeywell DS06

No mention of leaving the valve off after installation and filling?

Watts does mention a LWC

Could not get to the I&O for the Apollo FF12, another common brand.

B&G seems to be the only one I found with the "valve off" instruction?

Zman

Jean-David,
The original article is almost entirely factual . The only opinion expressed is the need for LWCO. Hard to argue with that.
This has been a very interesting conversation. In my mind the answer is "it depends"

Ice,
On a larger scale, I walked into an underground garage with a freshly power washed floor. The first thing I noticed was the sweet smell of glycol. The system held about 500 gallons.
It is always a good idea to cap boiler drains and tighten them with a wrench. In some cases we have removed the handles. Clearly marking the correct place to connect the water hose is also a good idea.

Carl

icesailor

Carl.

I mentioned this story before. Someone had a house freeze up where the baseboard on the third floor froze up and broke next to a knee wall. The owner was away for the winter and someone was supposed to watch the house. They didn't. The water ran and the heat ran, and the hot, moist water caused all the wood trim to turn black. Then, the sheet rock ceilings all fell down. The oil company made regular deliveries until the water in the cellar got high enough to short out the boiler. No more heat. No need for more deliveries. Then, the well pump finally shorted out. That was in a cellar that finally had 28'X 60'X4' of water in it by the time the water stopped running. The woman came back late one evening on the last boat, went home and found that. She had a nervous breakdown and they had to cart her to the hospital for the night and a few nights more. Insurance was picky about the claim because the "friend" hadn't been doing "Due Diligence" in checking the house.

Then, there was a similar one where the same size cellar had 6' of water in it. The caretaker claimed he had inspected the house 6 hours before. He blamed the Plumber. The owner and the Insurance company were preparing to sue the plumber for some long ago connection.

I saw the plumber one day. I asked him if he knew how to calculate when the Caretaker was there last? He asked me how. I told him to calculate the cubic feet of the volume of the cellar and divide it by 7.44 (7.44 gallons in a Cubic Foot of water) and divide that by how much water can a 12 GPM/ 720 gallons per hour pump deliver in 24 hours. (Hint: No where near enough water to fill the cellar with 6' of water in 6 hours.

"EFF" Caretakers.

ahappydancer35

Been in the business over 40-years and seen both sides of this issue but what I've never seen is a closed loop system that NEVER leaks! They all suffer some pressure loss if left to themselves long enough. Sometimes people miss the minor point that homes are designed to be occupied. So chewing fingernails over pipes bursting and flooding the house doesn't make much sense in my experience. All of the flooded homes I've seen are the direct result of the house being unoccupied for a lengthy period of time (days upon days, if not weeks). If we're going down the path of trying to keep the system pressure stable for the life of the home, then we would do better to abandon the diaphragm expansion tanks and go back to the old hollow tanks. At least the bladder won't rot out and cause a sudden loss of system pressure.

I've never, in all my years, seen a closed loop hot water boiler so hot it would crack if cold water were added. I have, however, seen steam cast iron boilers dry fired and cherry red and even after admonishing the client to NOT put any water into the boiler, they did and it cracked. Human intervention always creates the greatest problems. But a water boiler with a working high limit will always have water in it unless it's the source of the leak. A failed bladder expansion tank combined with a lack of fresh water to the heating system will drop the system pressure substantially. An uneducated service tech will see the low pressure and dutifully add water to bring the pressure up. And leave. Now when the system gets cranking and in the absence of a working expansion tank, you've got a sudden pressure increase from the expansion of the heated water and now the relief valve has a job to do and does it, dumping the excess water. Boiler pressure goes down. Heat may stop on the upper floor(s). Pipes an freeze. Not a good situation. I've dealt with numerous failed diaphragm tanks and auto-fill valves left on. The call is ALWAYS water on the floor around the boiler. No damage. Just some water on the floor. A new relief valve, a new expansion tank, sometimes a new float vent and sometimes even a new auto-fill valve. But other than the bill, the damage is never an issue.

So my vote, leave the auto-fill valve turned on. It's designed to be on and it has a job to do. If properly installed, there's no issue. Some of the modcons of today actually have their own on-board auto-fill valve included. Good luck getting warranty on one of those puppies should the boiler dry fire because the manual valve was turned off! Stop dreaming up disaster scenarios and let the devices do the work they are designed to do. And in any event, a LWCO is always an added line of defense.

Robert O'Connor_12

Mine is closed.

Gordy

Mines closed, has not leaked in 62 years.

Bob Bona_4

I'm in the open court. If it's gonna be closed, why bother installing one? IMHO of course.

hot_rod

Leave the fill valve out of the system, and save the cost of the BFD (back flow device) which is pretty much required with every fill valve.

Probably more back flow leaks than any valve in hydronics. Especially when they are valved off

SWEI

If the system turns out to need a quart or two of water every year, and the boiler should really be serviced (or at least checked) once a year, I'm perfectly happy trusting the LWCO or onboard low pressure switch in the boiler to do its job. When we visit a job once per year and keep notes, we have a pretty good idea what's going on there -- and that helps me sleep.

Docfletcher

Hot Rod, My BFP will leak boiler water from vent with the ball valve before the BFP off. I plugged the vent. Now boiler has no pressure pressure loss.

hot rod said:

Leave the fill valve out of the system, and save the cost of the BFD (back flow device) which is pretty much required with every fill valve.

Probably more back flow leaks than any valve in hydronics. Especially when they are valved off

icesailor

A lot of guys install a shut off ball valve AFTER the BFD and Fill Valve. Then, they shut off that valve. So, the BFD doesn't "see" the differential pressure and allow water to drip out the air vent hole. Both valves need to be closed. And because the BFD is equipped with Unions, it is really easy to service the devices without draining the boiler. Unless you use a steel/black nipple between the copper pipe/brass adapters and the valve. Then, the nipples turn into sinking ships.

Zman

Docfletcher said:

Hot Rod, My BFP will leak boiler water from vent with the ball valve before the BFP off. I plugged the vent. Now boiler has no pressure pressure loss.

Did you go ahead and cap those pesky T&P valves that keep leaking? And that high limit switch and LWCO!
While you are at it, there is nothing more annoying then the seatbelt buzzer and the airbag light in your car.Better take care of them as well.
Man if I hear that CO detector go off one more time I'm going to... I don't smell anything, do you?

These are all safety devices that should be kept in tact. You should not plug the vent on your back flow (or any of the other suggestions above).
Carl

Docfletcher

Zman, I hear you, and I agree in principle. The street pressure ball valve being closed takes over the job of the BFP. I don't have room for a ball valve after the auto fill, so I cant close of the supply there. I want the supply to the boiler closed off, and most certainly I can't allow the vent to drip boiler water. I think I read on the Cash Acme website that the BFP requires pressure on both sides to work as intended.

icesailor

Docfletcher said:

Zman, I hear you, and I agree in principle. The street pressure ball valve being closed takes over the job of the BFP. I don't have room for a ball valve after the auto fill, so I cant close of the supply there. I want the supply to the boiler closed off, and most certainly I can't allow the vent to drip boiler water. I think I read on the Cash Acme website that the BFP requires pressure on both sides to work as intended.

That's right. You need pressure on both sides. Or it will leak. Change it so there is a valve on the boiler side and the BFD won't leak.

DanHolohan

Back in my rep days, we sold BFP and I found that the RPZ types spit when they came before the PRV. The water couldn't get through the PRV fast enough and the backpressure caused the RPZ to spit. We solved the problem by installing the PRV before the RPZ.

Zman

Dan,
How would the PRV "See" the pressure on the boiler side? The PRV cannot do it's job with that configuration.

On homes where the owner turns off the domestic water when they are not in town, putting an additional spring check before the RPZ and PRV solves the issue with the weeping vent as the RPZ does not detect the lower pressure on the domestic side.

Carl

DanHolohan

We'd set it a few psi higher to compensate for the pressure drop of the RPZ.

hot_rod

Most PRV need 20 psi, some require 25 psi to seal the center passage, which closes off the drain port.

Usually when they spit a fast closing valve in the piping system causes a water hammer and a short spit. Solenoid valves, sometimes even flushometers. Or the incoming pressure drops below 20 psi

Harvey Ramer

I leave mine open. That's just what I do.

I often thought a smart fill valve should be built. One that can mechanically trip to the closed position in the event of a sudden downstream pressure drop. A pair of contacts could even be built in to shut down the boiler and turn on an alert light. In a pumping away scenario, it would also trip if you had a failed expansion tank.

PRV's already work off of downstream pressure. I don't suppose it would be really hard to build a device like that, that is entirely mechanical. Of course it would need an override for system filling.

I would be buying them.

Harvey

SherlockOhms

j a said:

I see no reason to ever leave it open…once the system has been completely full….I am sure you will get the opposite opinions…People don’t ride around with hoses attached to there cars radiator…Its foolish not to look at your system every couple of days…Why wait for it to call you,that usually means trouble…Pretty simple

If no low water cutoff is used it will have a thermistor or limit of some type. The only time I see them left open is if its leaking.