Resideo TK30PV125SFM/U TK30 Boiler Trim Kit with 1.25" Sweat SuperVent, FM911 Combo

The TK30PV125SFM is a TK30 boiler trim kit from Resideo (Honeywell Home) — 4.4 gal expansion tank.

A boiler needs the same four things at every installation: somewhere for the water to go when it expands, somewhere for the air to go, a way to fill, and a check so the fill cannot run backwards. A trim kit is those four parts matched to each other and bought once, instead of four line items that turn out not to thread together.

The expansion tank is the one that gets sized wrong. Water expands about 4% between cold fill and operating temperature, and it is not compressible — without somewhere to go, that expansion becomes pressure, and the relief valve becomes the expansion tank. A relief valve that weeps every afternoon is almost always a tank that is too small, waterlogged or set to the wrong precharge.

This kit carries a 4.4 gal tank with 2.5 gal of acceptance volume — acceptance being the part that matters, since it is how much expanded water the tank can actually take before pressure starts to climb.

The kit is built around TK300-30, PV125S, SCV-050, FM911.

Sweat joints are soldered. It is the cheapest connection in parts and the one that needs the pipe dry and the flame allowed.

Set the tank precharge to the system cold fill pressure before the tank goes on the line. A tank charged at the factory default on a system filled to something else is a tank working at part of its capacity from day one.

We stock these kit parts individually too: PV125S, SCV-050.

• Brand: Resideo (Honeywell Home)
• Manufacturer Part #: TK30PV125SFM/U
• Type: TK30 boiler trim kit
• Includes: TK300-30, PV125S, SCV-050, FM911
• Tank volume: 4.4 gal
• Acceptance volume: 2.5 gal
• Tank diameter: 11 in
• Tank height: 15 1/2 in
• Connections: Tank: Male NPT; SuperVent: Sweat
• Connection sizes: SuperVent: 1 1/4 in; Tank: 1/2 in
• Maximum temperature: 240 F
• Maximum pressure: 100 psi
• Category: Boiler Trim Kits