Hydronic heating system device dripping slowly - why?

[geoffhazel]

I have a hydronic heating system that was installed 20 years ago. This is a shot of the water "fill" line. It has valves on either side of some brass thing with an outlet on the bottom. That outlet is dripping water at the rate of 5 drips a minute - pretty slow, but more than it has in the past. I don't know if there's something I should/could do to get it to stop, or if it needs to be replaced. The water source is on the left side and the destination is on the right.

20190308_125513

• geoffhazel
• Mar 8, 2019

water fill line for the boiler

 

[Diehard]

That appears to be a "Reduced Pressure Zone Backflow Preventer"(RPZ).

If I am correct, this unit is required to be tested periodically by most, if not all jurisdictions throughout the country.
This device is typically required for "High Hazards" levels.
Is this a residential application?
Do you use chemicals in you hydronic heating system? For example antifreeze or additives?

Is it dripping constantly, around the clock?

Inside it has 2 spring loaded check valves and are capable of being repaired with rebuilding kits. (Not cheap!)

I'm very curious about this and once I post this response, I'll be searching Seattles' requirements for RPZ. Maybe they're very strict for some reason. Or maybe the installer installed something that was not required. Typically what is called a "Dual Check Valve with Atmospheric Vent" is required on residential boilers.
The reason I'm getting into all this detail is because if it's not required, I would recommend replacing it with the much less expensive Dual Check Valve with Atmospheric Vent.
You could simply call and ask your water purveyor if it's requirement.

 

[geoffhazel]

I'm not in Seattle, but in the city of Bellevue. The fellow that installed it was based in Seattle at the time. We don't have any fancy chemicals, just run plain water in the boiler/heating system and of course if we lose some, this fills it back up again automatically. It has never been "tested" and I was given no instructions to do any periodic testing at the time it was installed. (We moved in in 1997 and the house had electric baseboard heat. We wanted to convert to natural gas, and due to the way the house is built, there is no room for ducting; we had to go hydronic because it was the only possible way to move the heat around the house. )

If I was to call my water supplier, what exactly would I ask them? "Hi, on a hydronic heating system in Bellevue, what requirements are there for plumbing or check valves the water re-supply line?"

And to answer the other question, as far as I know it started dripping recently. We had some issues with the boiler that kicked off the over-temp-pressure valve, (since corrected) so there would have been some re-filling necessary. As far as I know it's dripping 24/7 at a slow rate.

 

[Diehard]

I just read some stuff from the Seattle Public Utilities. Very poorly written!

Hi, on a hydronic heating system in Bellevue, what requirements are there for an automatic water feed system.

Chances are they will ask what you currently have.
You could answer, "I have a PRV(pressure reducing valve) following some type of backflow preventer that is dripping water from an outlet on the bottom."
That would be describing either a RPZ or a Dual Check Valve with Atmospheric Vent.

The worse that could happen is that an RPZ IS required in your area. That would mean that they must be aware of it so that they or an approved tester can test it. (Typically annually, at a cost.)

Hopefully, it's like most of the rest of the country and only requires "Dual Check Valve with Atmospheric Vent", which is a non-testable device.

If you want, you could ask some friends and neighbors, that may be a bit more familiar with the required device in your area.

FYI- The "Dual Check Valve with Atmospheric Vent" device is typically provided for
Residential (Low Pressure Heating Boilers) having no chemicals added.

Feel free to ask any questions that come to mind.

Please let me know what you find out.

 

[frodo]

I would start by opening those little valves. you can open them with a screw driver
let it blow out any trash. then if that does not work.
take it apart and clean the springs and things of the debris that has accumulated in 20 years

DO NOT USE PIPE DOPE, use Teflon tape, pipe dope will gum up the innards
ask me how I know

 

[Diehard]

Keep in mind that a total repair kit for that RPZ would cost about $100 +/-, while a brand dual Check Valve with Atmospheric Vent device is likely 1/2 that cost.

But like I said you really should find out what is required in your area. It should not be an RPZ!

I suppose it wouldn't hurt to try clearing out any debris that may have lodged in the seats.

I originally had said 2 check valves, but actually there are 3. One on the inlet side, one on the downstream side and one on the bottom for dumping. The one on the bottom is suppose to open when it senses a difference in upstream and downstream pressure. Each check valve has a different spring value, and they are subject to fatigue.

The reason I had asked, "Is it dripping constantly, around the clock?" was because if it was off and on, it could be caused by one or more minor water hammer events, affecting the pressure balance within the unit.

They are rather sensitive and that's ONE of the reasons they are required to be tested, (typically) annually.