Closed plumbing systems & expansion tanks

[Joe Funderburk, CMI]

A builder of a new home is claiming that there is no backflow preventor present on the home and thus no expansion tank is required.

Isn't a backflow preventor integrated into this pressure reducer? Notice the one-way arrow.

[Joe Funderburk, CMI]

Hello Tokyo! Any plumbers awake tonight?

[Bruce A. King]

I thought those were one way too, and how does the builder know the city does not have a check valve at the street?

[Joe Funderburk, CMI]

How can it possibly reduce the pressure if allows backflow to the street system? I think the builder is blowing smoke or ignorant of these valves.

[Bruce A. King]

I linked this thread over to IN and Jerry over on Inspection News found a technicality (imagine him doing that) with your post Joe.

An expansion tank is not required.

An approved device for thermal expansion control is the correct phrase.

Lots of posts over there but no one has come up with a model number of your valve and data sheet yet, got any numbers?

[Joe Funderburk, CMI]

Originally Posted by bking

I linked this thread over to IN and Jerry over on Inspection News found a technicality (imagine him doing that) with your post Joe.

Seems all NACHI's forum is good for these days is chatter about inspection agreements, how to get paid, and politics.

In 2 days, you're the only one who has replied to this post, which I think should have created a good technical discussion.

Guess I'll be spending more time at Inspection News. Thanks Bruce. I've changed my wording.

Here's a tag that was on the valve. I've already researched it. It's apparently an Apollo valve. I could not get any technical info about how it functions.

[mnahrgang]

Be patient. It may have been two days, but I just now looked at your post. If I had an answer for you, I would give it, but I don't know. Someone else will likely be along. Business is picking up. Remember IN is full of out of work ASHI guys, so obviously they would post more.

[Bruce Thompson]

Originally Posted by mnahrgang

Be patient. It may have been two days, but I just now looked at your post. If I had an answer for you, I would give it, but I don't know. Someone else will likely be along. Business is picking up. Remember IN is full of out of work ASHI guys, so obviously they would post more.

ouch! hey that hurt!

I'm not an ASHI member and I've had a good year!

I too can't help on the thread -- sorry

[Bruce Thompson]

OK, maybe i do.

Aren't most pressure reducers installed a certain direction because of the size of the adjustable orifice on the downstream side? Therefore, there is not a backflow preventer built into the device.

Is that what you're asking?

[mnahrgang]

Originally Posted by bthompson1

ouch! hey that hurt!

I'm not an ASHI member and I've had a good year!

I too can't help on the thread -- sorry

I did not intend to hurt or offend. If I did, then I sincerely apologize.

[Joe Funderburk, CMI]

Originally Posted by bthompson1

OK, maybe i do.

Aren't most pressure reducers installed a certain direction because of the size of the adjustable orifice on the downstream side? Therefore, there is not a backflow preventer built into the device.

Is that what you're asking?

Thermal expansion control is required for closed systems. If there is a pressure reducing valve present, that means it's a closed system. Correct??? How can the pressure be regulated and the system be open to the street? I don't think that is possible.

Whether or not "back flow prevention" is present is probably not what I mean to ask. What I mean to ask is whether the presence of the valve pictured means the system is closed and thus requires thermal expansion control.

[Brian E. Kelly]

http://www.apollovalves.com/_docs/cat_PHBRWPRV.pdf

THERMAL EXPANSION CONSIDERATIONS

Installing a pressure reducing valve creates a closed water system. Thermal expansion occurs
in a closed system when water is heated and pressure builds up. A thermal by-pass designed
into the reducing valve can dissipate the expanded pressure back to the service main.
When the system pressure in a closed system increases to a pressure greater than the supply
pressure by just one pound, the o-ring on the stem will flex (see Fig. A) and allow the excess
pressure to be relieved to the supply side until pressures on both the system and supply sides
are equal. When a faucet on the system side in used, thus lowering the pressure, the valve
opens as soon as the system pressure falls below the set outlet pressure, typically 50 lbs.
The valve and the system then return to normal as shown in Fig. B above. The PRVH features

a ball and seat type of check valve as a thermal by-pass but the principle is similar.

[Bruce A. King]

Good info, thanks!

But that does present another question, I believe Joe was told by another inspector that we know, that he monitored the pressure on a house that had one of those valves and saw it skyrocket while the cold water tank was heating, with no hot faucet open anywhere.

[Joe Funderburk, CMI]

Originally Posted by bking

Good info, thanks!

But that does present another question, I believe Joe was told by another inspector that we know, that he monitored the pressure on a house that had one of those valves and saw it skyrocket while the cold water tank was heating, with no hot faucet open anywhere.

If the street pressure is 110 and the house pressure is 60, if turning on the water heater raises the house pressure to 111. At that time, the pressure reducing valve opens to equalize the street and house pressure (at 110). Therefore, the house pressure can indeed skyrocket until it equals the street pressure or until a valve is opened at the house to bring it back down to 60. That's how I read it.

[Bruce A. King]

That would explain why the plumbers are now installing some other expansion device, besides its required now.

I see a lot of those small thermal relief valves with the small clear tubing for the discharge line. Lots cheaper than the blue tank method.