New pressure regulator not regulating pressure

[Tyler S]

Recently I had hot water holding tank installed to add a reserve to my oil fired boiler. I noticed we were getting water hammer afterwards. I checked the pressure at the sillcock and was reading 100+ psi with a 40 psi drop when a faucet opened. We have city water and it appears to enter the house at 125 psi. I changed the pressure regulator and added a 0-100 psi gauge downstream. The pressure not only wont hold but seems like there is a surge hammer as well as a stopping water hammer. I have the psi in the expansion tank at 60. Valve is oriented correctly. Could I have a bad valve? Could I have ruined it during install? I'm at a complete loss. Thanks in advance

 

[bud16415]

There is always the possibility of getting a bad part off the shelf. It is also possible something got damaged during the hook up. Without seeing it, it is hard to say. One thing I have seen before with valves and pressure devices is if you get debris in there or shook lose in the line they can get stuck. Another is if Teflon tape was used and left too long on the end of a fitting that can come off and clog/stick something.


You said you added a holding tank for the hot water to add capacity. What type of tank was it? Maybe add a couple photos or a sketch.


And also welcome to the forum.

 

[Diehard]

What make and model PRV(Pressure Reducing Valve)?
What was the preset pressure setting from factory?
What pressure are you getting that's not holding?

What is happening when you get "surge hammer as well as a stopping water hammer"? (Not sure what the you feel the difference is.) Are you aware of what's changing the flow velocity? Is it the pump, between the boiler and the storage tank, starting or stopping?

Where in the system is this expansion tank you speak of? That air pressure is typically set at the service water pressure and must be pressurized (as you may already know) when it's completely isolated from the water pressure.

Was the 100+ psi reading at the sillcock before of after the 40 psi drop when flowing? Somewhat inconsistent with the 125 psi entering the house. In other words at a static condition(no flow) the pressure doesn't change except when at different elevations.

 

[Tyler S]

Watts LF25AUB
Pressure was set at 50 from the factory.
I dropped the expansion tank on pressure to 13 psi. It is installed on the hot water lines for the baseboard heat.
I have static pressure at 55 psi. Which gives me about 45 psi when flowing.
The surge sounds the same as the stop. I'm pretty sure it's the gate check at the holding tank slamming shut. I can physically see the pipe shake when a faucet is opened.

I'm positive it's the recirc pump that is pressurizing the cold. After the boiler fires and then stops, the pump is running. I can see the pressure rising past static setting at the valve. If I close the ball valve downstream of the prv and pressure gauge, the pressure stabilizes. As soon as I open the the ball valve downstream of the gauge, the pressure surges and will continue to rise as long as the pump is running.

The photo close up of the boiler shows the hot line from the bottom of the holding tank that ties into cold water feed for the boiler. I feel a hot cold mix as I move up the line marked in blue. That is where I think I need another check and expantion tank. I'd like to put them between the two T's.

The 100 psi was before the 40 psi drop.

 

[Diehard]

I'm a bit confused. Here's my take...

You have an oil fired boiler apparently equipped with a tankless water heater, which provides domestic hot water, at your domestic water pressure, and in the absence of a visible tempering valve, at close to the same temperature your heating water is set at.

You circulate that water to a storage tank that stores that water and maintains a temperature at a preset temperature based on a temperature sensor located at the storage tank. What temperature do you have the storage tank/circulator set for? I can see you are tempering the water as it leaves the storage tank to prevent scalding.

The best I can tell the, PRV behind the boiler is the one used to reduce the cold water pressure to the heat exchanger(tankless unit) in the boiler. Your 50/55 psi system. (I'm not sure why here and not for the entire house.)

So that leaves the PRV you show by the oil tank, the low pressure makeup for the heating system.

Does this make sense?

In any case, what I see so far is you have a closed loop system, subject to heating and expanding water (raising the pressure based on differential temperatures it sees), but no room for expansion. So YES you are missing an expansion tank.

Your heating system expansion tank has nothing to do with the domestic hot water side of things.

 

[Tyler S]

Yes it makes sense.
I now understand the heating system expansion tank has nothing to do with DHW. Which is why I brought it back down to the 13 psi. The prv behind the boiler is set to run at 12-15 psi. At least that's what its tag reads. But hard water could be causing it to have issues. I already changed the pressure relief valve that was in bad shape with scale.

When I install an expansion tank, should it be in the area where the line coming back from the holding tank tees into the cold water feed for the tankless water heater? Do I need a back feed prevention valve or check valve? Not the same thing correct?

I'm thinking a 1/2" spring check valve, downstream of a 2 gallon expansion tank inflated to the same static pressure of the PRV on the main supply. Does that make sense?

The thermostat for the circulator I thought was set by the aquastat on the boiler. 160-180 degrees.

Just to be clear, the 55 psi PRV is the main feed for the whole system by the oil tank. The low pressure PRV is the one over the boiler.

 

[Diehard]

Well I don't have time right now but here goes.

I couldn't follow the piping connections very well and apparently misread them if that PRV behind the boiler is the low pressure unit. As it appeared to be feeding the domestic water side and not the heating water side. It was pretty tough to see exactly what was connected to what.
I'm no expert but one thing that bothered me was the fact that you are feeding full boiler water temperature to your storage tank. I thought that typically the water was stored at the final desired temperature. Which would mean the water must be tempered as it comes out of the boiler, as it typically is. By removing the tempering valve at the boiler and storing the water at a much higher temperature, and tempering it after the storage tank, does of course allow you to have more tempered water available to you. But something just isn't right about that.

A common accepted approach is to use what is called an indirect water heater such as one called the "SuperStor", which you are probably aware of already. he heat exchanger is located within the storage tank rather than in the boiler.

I'm not so sure what your using for a storage tank is designed for those higher temperatures.

You may want to post this on the plumbing forum site. https://www.plumbingforums.com/

Here's the SuperStor...


How long have you had your set up?
I assume you designed it?

 

[slownsteady]

Can we assume you bled out all the air after you plumbed in the new parts?

 

[Tyler S]

I did not design the set up. The tank came with a recommended design. My brother in law installed the unit and customized it to fit our system. He is a licensed hvac tech. It was like pulling teeth from a honey badger just to get him here. So I dont want to bother him. I'm capable of doing the work I just want to run my thoughts by people with more experience so I dont **** it up.

We've had it for maybe a month and I'm 100% confident there is no air in the system. I'll take more pictures tomorrow. Unfortunately this site compresses the images so you loose a lot of clarity when you zoom in.

I appreciate all the time you've taken to help me so far!

 

[Diehard]

I did not design the set up. The tank came with a recommended design. My brother in law installed the unit and customized it to fit our system. He is a licensed hvac tech. It was like pulling teeth from a honey badger just to get him here. So I dont want to bother him. I'm capable of doing the work I just want to run my thoughts by people with more experience so I dont **** it up.

We've had it for maybe a month and I'm 100% confident there is no air in the system. I'll take more pictures tomorrow. Unfortunately this site compresses the images so you loose a lot of clarity when you zoom in.

I appreciate all the time you've taken to help me so far!

I'm in bed right now but it sure would be nice to see the recommended design the tank came with.

 

[Tyler S]

Here it is.

 

[Diehard]

Yes that diagram, does in fact, confirms that storage tank was designed for that setup.

So you're saying that "The prv behind the boiler is set to run at 12-15 psi." Or in other words the heating system pressure, for feeding the heating system make-up water.
Why does it look like it connects up to the domestic water (high pressure) system, in this picture? What am I missing here?

Where does the PRV near the oil tank tie into the system?

And yes, the cold water makeup line which provides makeup water to the boilers heating system typically requires an approved Backflow Preventer, which is different than a single check valve. It has a higher level of protection and is called a "dual check valve with atmospheric vent". It is typically install just upstream of the PRV as shown here...

 

[Diehard]

You had mentioned, "The thermostat for the circulator I thought was set by the aquastat on the boiler. 160-180 degrees."
Both your pictures, as well as the diagram, shows an immersion aquastat on the storage tank for control of the circulator.
Whatever difference or variance in water temperatures that storage tank is subject to, is what is causing an expansion and resulting rise in pressure. It wouldn't take much when it has no place to expand to, hence the reason for a rise in pressure.

 

[Tyler S]

So were moving in the right direction!

The prv above the boiler does in fact tie into the domestic cold.

The prv by the oil tank is the main feed from the city supply. Pipe comes in through the wall, then the main shut off, then the water meter, then a gate check valve, then a gate valve to draw down the system, (this was all here when we bought the house). Then ball valve, then the prv to reduce city supplied 125 psi to 55 psi. That line feeds the house with cold water.

It's difficult to see in the pictures, but that line runs the cold to the rest of the fixtures in the house. It also runs to the prv above the boiler to feed the heating system. It also runs to the lowest point in the boiler for the domestic hot water.

I do not see a backflow preventer, resembling the one in your schematic, anywhere in my system. Only the gate check valve by the meter. Just upstream of the prv by the oil tank.

I saw the aquastat in the schematic on my holding tank. I looked in the box but I didnt see that it truely was a functional aquastat. Upon further inspection, it is!! Its set at 140.

So going forward, I'm not sure if the backflow preventer is necessary. Maybe its code now in CT? Can I get away with a spring check valve and an expansion tank where the hot and cold mix in the photo you referenced above? 2 gal expansion or can I get one of the mini tanks?

 

[Jeff Handy]

I am jumping in without reading the whole thread.
But a prv will often not function as a backflow preventer.
You can get the info off the valve, and check that out.

 

[Diehard]

We're missing something here.

Let me first ask, how is your domestic hot water pressure at your fixtures?

You say, "The prv above the boiler does in fact tie into the domestic cold." And you also said that it is set to run at 12-15 psi. When I said it looks like it connects up to the domestic water (high pressure) system, in this picture, I was referring to the downstream side of the PRV connecting to the domestic hot water, which should be full house pressure of 55 psi.
The 12-15 psi PRV is suppose to for makeup water to your heating system only.

The diagram I included above in Post #12 is the typical arrangement for makeup water to your boilers heating system, that would be set at 12 to 15 psi.
The water connection to your domestic hot water system should be from the 55 psi house pressure. That's why it didn't look right to me and was questioning whether I was seeing the piping correctly in the pictures.

I realize it can be difficult to describe what's happening sometimes. I would need pictures showing exactly what's happening from that first PRV, at the oil tank, all the way to the boiler connections. And/or a single line sketch showing interconnections of all piping and the devices, including Tees(not elbows).

You appear to have a single circulator for your house heating system, which appears to be on your return piping. Commonly the makeup water for your low pressure heating system is connected on the return somewhere. I don't see anything in the pictures showing that makeup water to your low pressure heating system. It must be elsewhere. ??

 

[Diehard]

BTW...I'm not sure if you're required to retrofit an existing system with that backflow preventer I show. Nor if your jurisdiction requires it.
I also have an oil fired hot water boiler with the tankless option for domestic hot water and do not have one either.
But the next time some work is done to it I will likely add it.

 

[Tyler S]

Let me work on a sketch.

 

[Diehard]

Let me work on a sketch.

 

[Tyler S]

Sorry for the long wait. I double checked my "schematic" it's correct as far as can tell. I omitted ball and gate valves valves for clarity. Locations are not exact except in relation to each other in terms of sequence. Let me know if I should add arrows indicating direction of flow. For anyone just reading this, the question I have is whether or not I should install a check valve and expantion tank at the locations in pink. I believe the circulator pump at the hot water holding tank is pressurizing my domestic cold water feed and I am experiencing water hammer. Thanks for your time.