Pressure Relief Valve for MasterTemp

[nostaljake]

My plumber says a pressure relief valve is required by code for a new heater. I've read previous threads on this topic and understand the official Pentair kit is the 460925. But it's insanely priced at almost $200!

I saw @ajw22 mentioned you can buy the parts separately at a plumbing supply store, so I'd like to go that route. I just want to make sure I get the correct items.

1. For the valve itself, the installation instructions says the relief pressure MUST NOT exceed 50 PSI. But should I go lower than 50 PSI? Is 30 PSI better or worse? What's a safe number here?
2. Am I correct that it needs to be rated for AT LEAST 400k BTUs if that's the size heater I'm getting? So over 400k is ok, but not under?
3. It looks like the official Pentair valve has some kind of nut on the inlet. Is this necessary for any reason?
4. Do I want to make sure the brass is lead free?
5. I'm assuming the lengths of the fittings don't have to be exact?

For example, would this combination work? relief valve + 3" fitting + elbow + (2x) 2" fitting

 

[ajw22]

Let's see what @swamprat69 thinks.

 

[Lake Placid]

So what you’re saying is that somebody’s life is worth less than $200 to you. Pressure relief valves are designed to prevent boilers, hot water heaters, and other pressure vessels from becoming a bomb in the event of a system component failure. Yes parts can be put together for less money…..if you know what you’re doing…you get the correctly engineered parts….and you assemble them correctly….it will work fine. It’s your money and your call for you to perform a cost analysis on the correct move for you to make on your budget vs someone’s life/safety.

Apologizes in advance for being debbie downer. Carry on.

 

[nostaljake]

So what you’re saying is that somebody’s life is worth less than $200 to you.

This is unhelpful.

I understand the purpose of a pressure relief valve. My plumber, a licensed master plumber, told me I should go to Home Depot and get the parts. I checked on TFP and @ajw22 said you can get the parts at a plumbing supply store.

If you think they are both wrong and everyone should just get the Pentair version, that's fine. But you can say that without being a d... let's say debbie downer... about it.

 

[JamesW]

You just need a 50 psi pressure relief with a rating of at least 400,000 btu/hr plus the brass nipples and brass 90.

https://www.pentair.com/content/dam/extranet/nam/aquatics/north-america/aquatic-systems-photos-and-images/pool-pad-pro/commercial-pool-products/heaters-and-heat-pumps/mastertemp/archive/2021/01/26/Manual-MasterTemp-Pressure-Relief-Valve-474451-English.pdf

https://www.supplyhouse.com/Apollo-Valves-1041710-3-4-MNPT-x-3-4-FNPT-RVW40-697000-BTU-Bronze-Relief-Valve-50-psi

Pressure relief valve qty. 1
• Brass elbow 90° qty. 1
• ¾" x 3.5" brass nipple qty. 1
• ¾" x 2.5" brass nipple qty. 1
• ¾" x 1.375" brass nipple qty. 1

Purchase separately and install a 3/4" pressure relief valve complying with the ANSI/ASME Boiler and PressureVessel Code, having a capacity equal to the Btu/hr rating of the heater. The relief pressure of the valve MUSTNOT EXCEED 50 PSI. The relief valve must be installed horizontally. T

 

[JoyfulNoise]

My plumber says a pressure relief valve is required by code for a new heater. I've read previous threads on this topic and understand the official Pentair kit is the 460925. But it's insanely priced at almost $200!

I saw @ajw22 mentioned you can buy the parts separately at a plumbing supply store, so I'd like to go that route. I just want to make sure I get the correct items.

1. For the valve itself, the installation instructions says the relief pressure MUST NOT exceed 50 PSI. But should I go lower than 50 PSI? Is 30 PSI better or worse? What's a safe number here?
2. Am I correct that it needs to be rated for AT LEAST 400k BTUs if that's the size heater I'm getting? So over 400k is ok, but not under?
3. It looks like the official Pentair valve has some kind of nut on the inlet. Is this necessary for any reason?
4. Do I want to make sure the brass is lead free?
5. I'm assuming the lengths of the fittings don't have to be exact?

For example, would this combination work? relief valve + 3" fitting + elbow + (2x) 2" fitting

That relief valve doesn’t look like it has an all brass body.

Just go to the hardware store or a plumbing supply store and get a standard TPV that you would install on a hot water heater. Most plumbing supply shops will have a dude behind the counter that you can ask for help. I get shopping on Amazon seems easy but there’s way too many cheap Chinese made knockoffs on there that are complete garbage. Gus with big beer belly and exposed butt crack sitting behind the counter knows exactly what you need …

 

[JamesW]

Apollo Valves 3/4 in. Bronze MNPT x FNPT 50# Relief Valve | Ferguson

Find the Apollo Valves 3/4 in. Bronze MNPT x FNPT 50# Relief Valve at Ferguson online for delivery or pickup at a Ferguson store near you.

www.ferguson.com

https://www.supplyhouse.com/Apollo-Valves-1040805-3-4-FNPT-RVW40-535000-BTU-Bronze-Relief-Valve-30-psi

https://www.pentair.com/content/dam/extranet/nam/aquatics/north-america/aquatic-systems-photos-and-images/pool-pad-pro/commercial-pool-products/heaters-and-heat-pumps/mastertemp/archive/2021/01/26/Manual-MasterTemp-Relief-Valve-474451-English.pdf

Pressure Relief Valve (P/N 473715) Qty. 1• Brass Elbow 90° (P/N 472619) Qty. 2• 3/4” x 3.5” Brass Nipple (P/N 474169) Qty. 1• 3/4” x 2.5” Brass Nipple (P/N 473689) Qty. 1• 3/4” x 2.0” Brass Nipple (P/N 473688) Qty. 2

473715Z | Pressure Relief Valve

Pressure Relief Valve

www.getpoolparts.com

 

[JamesW]

But should I go lower than 50 PSI? Is 30 PSI better or worse? What's a safe number here?

You can do 30 or 50.

If you have high system pressure like with an in-floor cleaning system, go with 50 psi to be safe.

 

[swamprat69]

Hot water heaters are essentially a closed system unless a hot water faucet/tap is open. Modern hot water boilers are a closed system with some style of sealed expansion tank although some older systems used an open tank at the highest point in the system just like some older toilets that had an open tank mounted on the wall above the toilet. Water is essentially not compressible, which means that when it is heated inside a closed system the pressure will increase exponentially as the temperature increases. That is why a temperature/pressure relief valve is required on hot water heaters and water boilers. In the older open tank boilers if the pressure increased the open tank would just overflow. The reason that you might need a pressure/temperature relief valve on a pool system which is normally an open system is if you had a valve on the outlet side of the heater or a heater bypass piped in it is possible that if the valve(s) is/are in the wrong position or an automated valve fails you can turn your normally open system into a closed/semi closed system and build up excessive pressure. I don't have any such valves in my system and feel completely safe with my Hayward gas heater as even if the heater pressure switch ( to confirm water flow and allow the heater to run ) were to fail in the closed position allowing my heater to run without the pump running it would require a total and absolute blockage of the heater outlet pipe to the pool in order to make the system a closed system.

 

[nostaljake]

You just need a 50 psi pressure relief with a rating of at least 400,000 btu/hr plus the brass nipples and brass 90.

Thanks for the help!

I believe this is the exact one from the photo you posted. It's the 50 PSI version with female inlet/outlet so it can attach to male brass nipples. Matches the item number from your photo too.

Seems to me I can get virtually identical parts to the Pentair kit for a fraction of the cost.