Hi All,

Been bz for a while, and vacationing. (the former a result of the latter:)

Anyway, in my mixed-use building there is a sewage sump which handles the ground floor. Because of a dip in the ground level between the building and the town sewer, I have to pump the sewage to the second floor, where it can drain to the town sewer line. There is a 2" force main running vertically from the pump for 2' then a ball type check valve, then 4' to the ceiling of the below-ground mechanical room, then across the ceiling to the service stack, then up the stack 10' to the ceiling, then into the ceiling and across to the main pipe, which goes across the breezeway and into my quarters to hook up with my sewer connection. (see photos below.)

The ground floor has a call center with a toilet room, an office with a toilet room, and a beauty salon which uses the common bathroom, also on the first floor, containing a coin laundry set, a toilet, and a (nice big)shower. The pump runs a lot, but mostly grey water.

When the pump stops, (which might happen a couple of times during a hair-washing session) the pipe bangs. The banging changes intensity. It is mentioned often in conversations with the owner of the beauty salon, (my daughter in law). When it gets really loud, she comes and finds me to tell me, and I go and shake the pipe above the check valve to reposition the pump in the sump. The toothbrush in the pipe hanger is there to lift the pump off the bottom of the sump, but not really, the bottom of the pump just brushes the bottom of the sump. When the pump sits on the bottom, and the pipe above is loose in the hanger, the banging does not change in intensity but remains at it's highest level.

As you can see from the photos, the piping joints have failed once _(the blue cement is new) pumping grey water into the adjacent office.

I have some issues with the install, (45's at the bends being the worst), but it seems to work. I am not convinced that this contributes to the hammering, rather, it is probably 14' of head stopping instantly when the pump quits. A soft start and stop pump would probably solve the problem, but I don't even know that they exist, and if they do... I'll bet they are pricy.

I have thought of putting a tee in the line and another tee to it with about 2' of capped pipe above and a piece of capped pipe below, but the air chamber would probably fill up soon. I could contrive a piston in the chamber, which should work.

I thought before I went to work on this solution, I should ask you fellas. It is entirely possible that you gurus might have a better answer.

Peter Legere
Consulting Visionary

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I think what I see, is everything is rigid. No flex anything to offset the vibrations of the pump.

Yeah, pretty much.

I see a number of things that can contribute:

1. There is nearly zero support. Use real pipe clamps, hangers using 3/8" rod, the equlivelent of Unistrut or whatever. This is extremely important in that short section above the pump.

2. Use a swing check valve at the first horizontal to eliminate the head problem.

3. Use two 45's rather than 90 deg whenever practical. Especially at the section above the pump.

4. Use a flex couplings to isolate the pump.

I may have found the solution to my problem. I went to the plumbing supply this AM to buy the fittings for my shock absorber, and there was a plumber being served at the counter. I described the problem and he said it was the torque of the pump that was causing it. Why that had not occurred to me is my shame. Of course! I am going to make a bracket to keep the vertical portion of the pipe rigid, and replace the 90 degree elbow at the ceiling with a piece of flex hose.

The plumber suggested I should replace the pipe from the pump to the check-valve with steel, but I will monitor the condition of the PVC for a while and replace if necessary.

The bracket will need to be easily dismantled for access to the sump for the ty jobs of maintenance. This should, at least, eliminate the possibility of flooding the main floor with grey water ever again.