Water Pressure on Fill Valve

spr1ggs_areus

Question is if I leave my shut off valve open will the resulting pressure damage the fill valve which is in the closed position. My Boiler system was built in 1952 and is copper in/under slab construction. Water is leaking out and I have to top off periodically. If the above is OK, then I do not have to keep turning off/on the shut off valve, just open the fill valve.

JUGHNE

What happens if all the water leaks out under the floor?
With the fill valve off then you have a dry fire boiler and possible explosion.
With the fill valve on you have a flood.

A low water cut off is the best insurance and then leave the water off. IMO

STEVEusaPA

JUGHNE said:

...A low water cut off is the best insurance and then leave the water off. IMO

That's the way I always do it. But you do have to check your boiler gauge, too.

spr1ggs_areus

My specific query has not been addressed. Here are more details. I have a 10 year old Viessman Boiler Vitogas 050, the specs of which does not mention an auto low water cut off, that I could find.
My pressure gauge tells me what I need to know re water pressure. System requires 12 psi. As stated there is MINOR water loss. I am getting ready to fire up the system for Winter. Yesterday the gauge was at ZERO after 7 months with Boiler turned off. Opened shut off valve, opened Fill valve and obtained the 12psi.
24 hours later it is at 9 psi. so I did the same today and boosted the pressure to 12. Bear in mind the system is still OFF, as I will not turn on until I return from Australia 2 days before Thanksgiving.
I suspect that there is less leakage when hot water is running through the system rather than no circulation with cold water.
So for several years I have been monitoring the gauge for loss of pressure and "topping off" when needed to get back up to 12 psi. So my question remains as before. One change to my outline is that there is the Backflow prevention device BETWEEN the shut off valve and the fill valve. From what I have surmised, there would be no damage to either the Backflow device or the Fill valve with the water pressure constant against it because of leaving the shut off valve Open. I am just looking for confirmation from experts that I am certainly not.
Thank you, Brian Peck.

Jamie Hall

No, there should be no problem with the backflow preventer or the fill valve holding against pressure. I assume that your upstream pressure is higher than your system -- boiler -- pressure.

So that is the direct answer to your direct question.

The loss of pressure in your system is indicative of a leak. A minor leak -- now -- perhaps, but a leak. Where it might be I haven't a clue. When it will create a problem for you I haven't a clue. You don't seem concerned about the problem of low water in the boiler, although that will happen to you sooner or later with more or less catastrophic results if you don't have a low water cutoff, but hey -- it's not my monkey, not my circus.

HVACNUT

A LWCO should have been installed with the boiler but add one. Then, find and fix the leak.