Heat Trap Water Heater Nipples and Expansion Tanks

Steamback

My dad always said there is no stupid question. But I feel this may actually be one...apologies.

Basically, all new hot water heaters have heat trap nipples on the hot and cold lines. Essentially check valves, correct?

Also, good practice says to install expansion tanks on heated hydronic systems.

My question is, how is one to add expansion capability to a water heater if the in/out connections are basically keeping water inside the tank?

ethicalpaul

They must not keep the water in the tank all the time or else you wouldn't get any water when you turned on the hot faucet in your bathroom

mattmia2

They allow flow in both directions, they just require a bit of pressure differential to open so they won't keep the system from flowing backward as the water is heated, they just stop gravity flow.

Jamie Hall

"Also, good practice says to install expansion tanks on heated hydronic systems."

Good practice? It's ,mandatory that there be an expansion tank, compression tank, or some other means to take up expansion.

Larry Weingarten

Hi @Steamback , I’ve got the dumb question… are we discussing hydronic space heating or domestic hot water? The answers depend 😉

Yours, Larry