This project explains how to replace a sewage pump check valve for a basement bathroom with a silent check valve to prevent water hammer noise, pipe rattle and vibration when the pump cycles. The new unit is an A.Y. McDonald Mfg. Co. 2068S – Silent Compression Swing Check Valve – Socket Ball Valve Combo.
Sewage Check Valve Water Hammer
I installed a standard or “non-silent” check valve/shutoff ball valve combo unit when I finished the basement bathroom 3 years ago. The sewage check valve has about 12 feet of water head – meaning it holds back 12 feet of water in the vertical piping to where it empties into the main sewer line under the 1st floor joists. When the sewage ejection pump shuts off, that 12 foot column of water tries to flow backward and slams the check valve closed with significant force causing a loud thump and shakes/rattles the PVC sewer pipe. This is known as a “water hammer”.
The water hammer is an annoyance but since the basement bathroom is used only occasionally, I wasn’t motivated to pull the sewage pump (yuck!) and replace the check valve…. until now because I noticed the water hammer and pipe shaking was causing the solvent weld PVC joint to fail and leak. It’s taken the 3 years for the pipe joint to develop a leak, which for the time being seems to have gummed up and stop leaking. I’m sure I’ll have a big problem if it’s not repaired soon.
This next video illustrates the water hammer problem. I wrapped a red 12 gauge electrical wire around the 2 inch PVC sewage pipe to better illustrate the shaking.
Jumping ahead, the new A.Y. McDonald Silent Check Valve eliminates the water hammer and causes very little vibration as indicated by the white electrical wire. The valve closes at the 1 second mark in the video:
My application is a bit extreme as the A.Y. McDonald 2 inch silent check valves are rated for 2 to 10 feet of static water head over the check valve, where I have 12 feet of static head. I called A.Y. McDonald to ask if this would be a problem and the product engineer said the most common problem is not enough static head (less than 2 feet) which won’t reliably close the valve. With 12 feet of static water head the engineer said I should be OK because the valves are designed with a margin of safety. He explained my other option was to install two (2) check valves spaced such that the static water head was between 2 and 10 feet. I chose to keep it simple and install the single check valve.
A.Y. McDonald – Silent Compression Swing Check Valve
The A.Y. McDonald series 2068S Silent Compression Swing Check Valve and shutoff ball valve combo is dissembled here to show the individual parts. The check valve is available by itself as the series 2067S – Silent Compression Swing Check Valve if you already have or prefer to use a different ball valve.
What I liked about the Silent Compression Check Valve are the black rubber gaskets and nuts that simply slide onto the 2 inch Schedule 40 PVC sewer pipe. The Compression fitting is a big advantage compared to a PVC Union with solvent weld pipe fittings in a sewage pump application because the compression fittings are easily removed leaving a bare pipe end. This means I can slide the sewage basin cover off the end of the sewage ejection pump stand pipe for maintenance. This point will become clear in later in this project when I have to saw off the solvent weld Union fittings on the old check valve.
Nested Flapper – Eliminates Water Hammer
What makes the A.Y. McDonald silent check valve different is the nested flapper in the top end that is key preventing the water hammer:
The swing valve in the bottom of the unit provides a water tight seal to prevent backflow:
Here’s the A.Y. McDonald silent check and ball valve combo beside the old check valve. It’s slightly taller but that’s not a problem because PVC pipe is easy to cut and fit.
This project is continued in How to Replace a Sewage Pump Check Valve – Part 2.
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