Pressure relief valve attached to Navien tankless is leaking....

jers5000

My pressure valve from my Navien combi boiler is leaking, but only when I open the pressure valve. In other words, when the valve is closed, no problem at all. However, when I open the valve to flush it/test it, water flows as it should through the pipe and drains out, but I also get a spray of water that comes out from the pressure valve itself. Any ideas? Thanks!

dko

Where from the pressure valve itself? At the threads that your pipe is connected to? Or from a crack in the body?

They are not expensive to replace and is not Navien specific. Just read the label so you get the correct one. The combi should have two relief valves, one at 30PSI for space heating side and another at 150PSI on the domestic hot water side.

jers5000

Thanks very much for your response - much appreciated. I've attached a picture here for reference. The valve that I'm speaking of is the one with the yellow tag hanging from it, and it is labeled as 150PSI. It is actually leaking directly from the handle that you left up to open up the valve - but only when the handle is actually lifted up. Otherwise, it doesn't leak at all.

On another note, I'm assuming that the other valve is the one that is located directly on top of the expansion tank - that too is labeled as 150 PSI. Is that an issue - should it be 30 PSI?

Thanks again!

EdTheHeaterMan

The outlet side of many relief valves is not water tight. There is no packing nut between the stem that is connected to the operating lever and the housing of the valve. The hole that the stem comes thru is pretty close tolerance but not air or water tight. That spray is normal when you test your valve as recommended. All that is telling me is that safety tubing that directs the flow to a floor drain or a visible safe place may have some restriction built in to it. You may want to check that safety tubing/piping to be sure it is installed according the the manufacturer's recommendations, and that the tubing/piping has no restrictions.

hot_rod

The valve on the potable water side of a combi is usually 125 or 150 psi.

On the hydronic side ut should be a 30 psi

In a tank type heater it would be a 150 psi 210 degree temperature snd pressure

jers5000

Thank you EdTheHeaterMan.

hot_rod, thank you. Does that mean that the silver piece on top of the expansion tank should be replaced to a unit that is 30 PSI instead of 150 PSI (which is what it says on top)? Or is there another release valve that I'm not seeing?

dko

There should only be one of each, the one on top of the unit should be 30PSI. If it's 150psi, it's definitely the wrong one.

hot_rod

Show a pic of the tank, if it is a DHW thermal expansion tank, it could have a 150 relief

The expansion tank in the above pic you posted is for the heating loop, the silver can is a float type auto air vent.

pecmsg

If it’s leaking it’s probably doing its job!

jers5000

@hot_rod - thank you! Was just coming back to post here that indeed, what I had thought was the pressure valve for the heating side was in fact the hy-lo vent with the 150 PSI rating! The pressure valve for the heating side is above the Navien and out of site, so didn't even know that it was there - but it is, and it reads 30 PSI.

One final question @EdTheHeaterMan and @pecmsg you had mentioned that if the valve is leaking through the handle/stem only when it's open, that it is likely normal operation since there is no packing nut. If the valve ever opens up due to the pressure (as opposed to me opening it up manually) can I expect leaking through the stem/handle then as well, or is that only when it's opened manually?

Thanks again all!

pecmsg

The valve should be exercised a few times a year. It is common for debris to settle in the seat and allow leaking. 

Open it fully for a few seconds and allow it to slam shut. 

You should have a gauge in the system to tell what’s going on. 

EdTheHeaterMan

One final question @EdTheHeaterMan and @pecmsg you had mentioned that if the valve is leaking through the handle/stem only when it's open, that it is likely normal operation since there is no packing nut. If the valve ever opens up due to the pressure (as opposed to me opening it up manually) can I expect leaking through the stem/handle then as well, or is that only when it's opened manually?

Yes the valve will leak thru the stem when ever water is being released at full open pressure. But I would not worry about that. It's only water and the majority of it will go thru the pipe connected to the outlet of the valve. That outlet is going to end up on the floor anyway. Unless the pipe goes to a floor drain. If the pipe goes anywhere else, like a place where you can't see it, or outside of the room where the relief valve is located, then the safety tube is not installed properly according the the manufacturer's instructions.

Here are the instructions that are attached to just about every relief valve you might encounter on your boiler or water heater



The important part of these instructions regarding the safety pipe is in yellow.
Discharge line must be as short as possible and be the
same size as the valve discharge connection throughout its entire
length. Discharge line must pitch downward from the valve and terminate at least 6" (152mm) above the floor drain where any discharge will be clearly visible


The other important part that everyone ignores is this:

WARNING: Following installation, the valve lever MUST be operated
AT LEAST ONCE A YEAR by the boiler owner to insure that waterways are clear


So at least you are operating that valve on a regular basis.

I can't tell you how many times I see the relief valve safety tube exit the building and end outside where a dripping valve can have an ICE DAM below freezing temperatures. That ICE DAM build up will leave the PRV useless since the ice dam at the end of the pipe will not allow water to exit if the valve opens because of an over pressure or over temperature condition. How can anyone think that is a good idea?

hot_rod

Have a new one on hand, it is not unusual for them to leak after you exercise them.