Water Pressure Reducing Valve - Signs of Failure ?

[Chefwong]

Just to bring this thread back to full circle...I've been observing this all winter.
It does appear that the water comes out the discharge of the PRV only when the boiler is in operation .

I have not opened the drain on the expansion tank in a couple years.
Should I do this in the off season ?

 

[Jadnashua]

Without rereading the whole thread...what kind of ET is in that part of the system? If it's a bladder tank, and you tap on it, does most of it sound more like a bell than a drum of water? You can't check the precharge without shutting down the system, but you could just put a tire pressure gauge on it. If, when you take the cap off, you get water, the tank is shot. If when you test for air, you get water out, the tank is shot. If you just get a reading, it should be the same as the pressure gauge on the boiler, but won't tell you if the precharge is correct, that can only be done when the other side of the bladder is open to the air, or at least can move the trapped water without there being any pressure against it from that side (i.e., a drain valve open).

 

[Sponsor]

 

[Chefwong]

Just one big steel drum.
Don't want to mess with it now...as then I'm going to have to bleed out every unit.

 

[Jadnashua]

If I understand what's there, over time, the water/air exposure will cause all of the air to be dissolved, often, creating rust in the system, and eventually, tend to waterlog the tank. A properly sized bladder tank will wear out over time, but in the process, won't be putting oxygen into the system to enable more rust to form. Over time, unless new water is added, all available dissolved gasses will have reacted (oxygen into rust). Those used to be common with wells. I guess, maybe also with heating systems before synthetic rubbers evolved and became fairly reliable. The magic is to drain them once a year to introduce enough air to act like a proper cushion during operation.

 

[Chefwong]

I used to drain it yearly. I forgot where I read it, but I interpreted it as there was no need to drain the tank yearly, as all I was doing was introducing the possibility of rust in the system, due to air in the closed system. Going to have to re-read your last response so it registers

 

[Jadnashua]

A bladder tank does not need to be drained...an air tank does because (at least as I understand it), the trapped air is in contact with the water...the air will get dissolved in the water, get carried around the system, and either rust things remote from it or get extracted by an air scoop or extractor. This will allow more water to be introduced to maintain the system pressure as air is lost. Because it is constantly adding air (including oxygen) into the system, it will cause more rusting than a bladder tank, where the air is isolated from the water. The tank you have may last a very long time, but does need to be maintained, and it creates a hit on the longevity of the rest of the system. If you replace a bladder tank when it fails, maybe every 5-10 years, if your system is tight, you're only adding a little bit of fresh water (and dissolved gas from the supply line), and things, in theory at least, should last much longer because there's almost no oxygen getting into the system, so there's little corrosion that can occur.