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# Boiler Bypass Water Flow Direction

Member Posts: 31

I have a WM WTGO 4 boiler from 2004. The boiler has 1 1/2 supply and return tappings . There are 3/4 tees on the supply and return pipes installed at the 1 1/2 tappings. The 3/4 tees are connected with 3/4 copper and a ball valve which is open. The circulator is located on the return side before the tee on the return side. I know this functions as a boiler bypass but which way does the water flow. Does the return side Tee pull hot supply side water in to warm up cold water from the return side or does the the return side water flow split between the boiler and the bypass pipe to slow the flow of cold water into the boiler. Supply tapping is at the top of the boiler and the return is at the bottom. Thanks.

• Member Posts: 23,905

Could be either one, depending on the various flows and other pumps in the system — and it could vary from time to time.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 208

" the the return side water flow split between the boiler and the bypass pipe to slow the flow of cold water into the boiler"

This^

The highest pressure in the system is immediately after the pump so the flow bypasses the boiler…………the amount dependent on the position of the ball valve that is in the line between the two T's. Note, however, that even with the ball valve fully open, the flow will be split between the boiler and the bypass. The amount of the split depends on the resistance in the boiler (minimal) compared to the resistance in the 3/4 pipe (also minimal at low flow rates).

• Member Posts: 31

LRCCBj

Thanks, I understand and agree. As to flow rates, the boiler supply is 1 1/4 " that splits into two 1" pipes that run the length of the basement with mono flo tees and regular tees suppling baseboard radiators on 2 floors and joining back into a 1 1/4" pipe to the return side circulator. Flow rates could be 8-10 gpm split through the boiler and bypass . Bypass is installed power WM piping diagram.