Thread: can anyone help with this one?

Closed plumbing systems & expansion tanks - InterNACHI Message Board


Please post comments over there or here whichever you like, thanks!

2003 IRC 2903.3.1 Maximum static pressure

P2903.4 Thermal Expansion
In addition to the required pressure relief valve, an approved device for thermal expansion control shall be installed on any water supply system utilizing storage water heating equipment whenever the building supply pressure exceeds the pressure-reducing valve setting or when any device, such as a pressure-reducing valve, backflow preventer or check valve, is installed that prevents pressure relief through the building supply. The thermal expansion control device shall be installed in accordance with the manufacturer's installation instructions.

Tell them to read the code. If the supply does not exceed the setting, why the heck have the valve there? The whole purpose is to lower the supply pressure to below 80 PSI.

If a PRV, check valve, Double check, Duel Check, and or a RPZ is installed a Expansion tank or an expansion relief device must be installed. If not the P&T valve will fail prematurely. I would post there but it will not let me.

Originally Posted by Bruce King

Closed plumbing systems & expansion tanks - InterNACHI Message Board


Please post comments over there or here whichever you like, thanks!

Bruce,

Instead of linking from one board to another, it would be better, especially for Brian, to copy and post your post here as well.

Never mind, I clicked you link and found it was not your post over there.

As much as I would like to agree that a thermal expansion tank is required ... I cannot because a thermal expansion tank is NOT "required".




A "thermal expansion control device" is, NOT ONLY a "thermal expansion tank".

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.

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

Quoted from the Apollo web page.

I'll repeat basically what Joe posted on the nachi thread since he made a good point that clarifies his writeup was correct and the builder was wrong.


Even though the pressure reducer has a thermal bypass built in, it is still necessary to have another thermal expansion device installed since thermal expansion can still cause the house pressure to go one psi higher than the supply pressure. All it does is prevent the 200+ psi condition that could occur if a near cold tank was heated while no one opened any hot faucets.


We have lots of homes around here with just the pressure reducer valve until around 2005 (depending on area) they started adding the tanks or the small PRV with a small clear discharge tube.

Originally Posted by Bruce King

I'll repeat basically what Joe posted on the nachi thread since he made a good point that clarifies his writeup was correct and the builder was wrong.


Even though the pressure reducer has a thermal bypass built in, it is still necessary to have another thermal expansion device installed since thermal expansion can still cause the house pressure to go one psi higher than the supply pressure. All it does is prevent the 200+ psi condition that could occur if a near cold tank was heated while no one opened any hot faucets.


We have lots of homes around here with just the pressure reducer valve until around 2005 (depending on area) they started adding the tanks or the small PRV with a small clear discharge tube.

Don't forget to look in the toilet tanks!

Vern, do you have a picture or link to the toilet tank version?


I have not seen one, I've seen those power flushers that scare the crap right out of when they go off!

http://www.watts.com/pdf/S-GOV80.pdf

Originally Posted by Vern Heiler

http://www.watts.com/pdf/S-GOV80.pdf

Vern,

Thank you, I had never heard of, nor seen one, before.

Cool product, have to look close to see the relief valve.

It won't work on a house that has a hot water recirc pump though, it needs to have one on the recirc loop since there is a check valve isolating it from expanding into the cold circuit.

What areas of charlotte have you found these in use?

I've found between 10 to 15 in random locations of 20 mile radius of Charlotte. Plumber neighbor said more expansion devices are being used because the expansion tanks have a high rate of failure. He says they have to replace a lot of tanks that leak. I've not seen one leak yet, but I don't ride in his truck?

Those tank bladders need to be checked also but you have to turn off the water, open a faucet, tear off the insulation thats wrapped around many of them and find the schrader valve.

Good info, first for me also.