Monoflo Know-How From B&G

Monoflo Know-How From B&G

Sixty years ago, long before the invention of baseboard radiation, B&G Monoflo tees made one-pipe hot water heating possible. Today, you can find Monoflo tees by the tens of thousands in American heating systems. They continue to work in their simple way, diverting some hot water from the main, through the radiator and back again. But as simple as they are, Monoflo tees often baffle installers, so we thought we’d take a moment to pass on a few tips your father may not have taught you.The rings go between the risers.
We put a red ring on one side of each Monoflo tee. That ring should always be between the risers that lead to the radiator. This means that if you’re using two Monoflo tees, they’d be facing in opposite directions. If you have a radiator that’s not heating as it should, check the position of the tees. If they’re facing the wrong way, the radiator won’t heat well. And check your circulator, too. It may be in backwards, too.


If you remove a radiator, don’t seal the branches.
If you cap the pipes that used to lead to the radiators, all the water will go through the run of the Monoflo tee. That increases the system pressure drop and slows the flow rate to the entire system.
If you remove a radiator, remove the tees as well. Or better yet, just connect the two branches with a short length of copper tubing. That way, the water that used to go to the radiator will still have a place to go.


On down-feed radiation, keep the temperature low to start.
Cold water is heavier than hot water. If you drain a down-feed Monoflo system and you’re having a tough time getting it to circulate again, try lowering the water temperature. This brings the density of the hot water in the main closer to the density of the cold water in the radiators and helps to get things moving. It’s an old-timer’s trick, and it works!

If air is a problem on start-up, raise the static pressure until you’ve cleared it.
More air will dissolve in water that’s under pressure. If you’re having a hard time getting rid of air on start-up, try raising the static fill pressure. The higher pressure drives free air into solution and brings it down to your air separator. Once you get the system going, lower the static pressure again. This is important because if you continue to operate at higher pressure, your compression tank may not be large enough for the system. Your relief valve will pop.

Pitch the main and the radiators up in the direction of flow.
This advice goes back to the original installation books of the 1930s. The pitch makes it easier to get rid of air on start-up. Check those pipes. They may have sagged as the years went by, and that can give an installer fits. If you’re having problems, always check the pitch.

Use the right amount of tees.
Radiators above the main usually work with one tee, and that tee should be on the return side. Radiators below the main always need two tees, and those tees should be the width of the radiator apart.
And keep in mind these rules apply to convectors and freestanding cast-iron radiators. The folks who invented the Monoflo fittings never imagined you’d be running 50 feet of copper baseboard from two tees piped six inches apart. The long run of baseboard puts too much pressure drop along the branch. The water responds by taking the path of least resistance along the run. The result? A cold radiator. And it looks just like an air problem!
If you have long runs of baseboard, run them as a separate zone.

Put your circulator on the supply, pumping away from the compression tank.
When you pump away from the compression tank, the circulator adds its pressure to the system’s static fill pressure. That drives air bubbles into solution and makes it much easier for you get rid of the air that appears when you start the burner. Usually, you’ll find you won’t have to bleed the radiators when you pump away.


Your local B&G Rep can be one of your best tools when you have questions about Monoflo or any other type of hydronics heating system. And they’re only a phone call away!

Reprinted from CounterPoint June 1995, Vol. 2, Issue 3

Alternate up and down.
If you have an up-feed and a down-feed radiator next to each other, the Monoflo tees should look like this: First tee (a standard tee) goes to the up-feed radiator. Second tee (a Monoflo) goes to the down-feed radiator. Third tee (a Monoflo) comes from the up-feed radiator. Fourth tee (a Monoflo) comes from the down-feed radiator.
In other words, you alternate the up and down connections. That produces more resistance to flow along the main and nudges more hot water into the radiators.