The lowest floor of my house which is below street level uses a sewage pit serviced by a Zoeller pump. The 3" pipe goes horizontal for 10', up for another 10' and then what looks like 15' to connect to the sewage line. Along the first horizontal 10' are a cast-iron check valve and shutoff valve.

My problem is this double bang (water hammer effect?) that this system seems to be having whenever the pump shuts off. The system always have a single small thud that we can hear on the floor above but this double slam is definitely something no one misses.

The biggest issue is that this double slam does not happen all the time. However it does seem to do it only when the pump hasn't come on for a little while. (It comes on at least a few times a day) Someone else commented in this forum on another thread about possible air coming back down the discharge pipe if the pump hasn't been used for a while.

Early this year I had to replace the mechanical float so I switched to a electronic float (the name escapes me). A few months later, the clamp that joins the two vertical pipes in the pit worked loose which I then messily fixed. Retrospectively, is this new slam/bang resulting in the clamp working loose?

So last week I brought in a plumber to look at it. He thought it was because the pit cover and subsequently screws were loose thus causing the noise. Despite my protests that they have been loose for years without a problem, I let him tightened them down. It didn't make any difference. His supervisor then took a look and suggested that the pipe be tied down to the joists so that the pipe do not move.

The next day, I worked with 2x4s, brackets and metal tape to connect the discharge pipe to the joists. As commented in a Sewage Noise thread in this forum, this made it WORST as the noise is now transferred to the floor above. Now it's like someones knocking at the door when the pump stops. This weekend, I'm going to untie the connections !

This is what I've done so far that hasn't worked:

- Tighten down the screws, pit cover, vent pipes on the pit.
- Repositioned the pump to more vertical align the discharge pipe.
- Added more pipe hangers with metal tape.
- Locked the pipe to the floor joists above. Worst now.

This are my available options for next steps:

- Leave more liquid in the pit to allow for more noise dampening and weight and higher run frequency? (The old mechanical pump had a more limited range so the pump was operating more often)
- Wrap rubber mats around all hangers
- Replace the check valve with a compression type fitting for greater isolation ?
- Add another check valve (3" valves seems to be rare and costly) ?
- Re-loosen up the pit cover fittings to allow for free movement ?
- Cut and add clamp with rubber fittings for noise isolation ?
- If it is air coming back down the discharge pipe, what is the fix for that ?

Plumbing experts, please help.

Thanks in advance.
Exhausted.

Bdbx, is there any type of a breather valve that could be installed to absorb the possible air coming back down the discharge pipe, (similar to an expansion tank on a heating system) or maybe have the sewer line snaked out to provide more open pipe space to allow air to reenter the pipe AS the waste is being discharged, rather than all at once after the waste exited to a more level pipe area that allows air to reenter the pipe . It seems that, as the waste is traveling through it 25' ascent, it is creating a negative vacuum/suction that creates a slam affect upon air reentry. Just athought, Good luck

DBDX18: There is a lot of sewage in that 3" discharge pipe. It weight quite a lot. You hear it when it falls down.

The "bang" noise is caused after pump shuts off and water that has been push upward the pipe now falls back on the check valve. When you attached discharge pipe to the joists you have made this noise more audible from obvious reason: pipe is touching house framing, bang produces vibration, and vibration now transfers into the joists. I would suggest you hang this pipe below the joists.

Proposed solution: I suggest that you install 2 check valves. They both should be the type with flopper inside, not spring loaded. Install one in the pit, about 6" above the pump on vertical discharge and the other one on top or the 10' riser, just before the pipe turns horizontal towards the street. I am enclosing simple drawing for better visual...

Also, make sure your transition 90s are long sweep 90s. Some loose parts, like pit cover, may contribute to the noise but are not the primary cause.

Let us know how you did... Milo

That's the theory talked about in another thread. I'm not sure how one can fix it if that's the case.

Quote:

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Originally Posted by rewes

bdbx, is there any type of a breather valve that could be installed to absorb the possible air coming back down the discharge pipe, (similar to an expansion tank on a heating system) or maybe have the sewer line snaked out to provide more open pipe space to allow air to reenter the pipe AS the waste is being discharged, rather than all at once after the waste exited to a more level pipe area that allows air to reenter the pipe . It seems that, as the waste is traveling through it 25' ascent, it is creating a negative vacuum/suction that creates a slam affect upon air reentry. Just athought, Good luck

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Thanks Milo,

Your diagram pretty describes my setup to the tee. However, I have limited access to the vertical pipe especially at the 90. This pipe actually goes through the drywalls and empty spaces and through the middle of the house! So that's no chance of straightening out the right angles.

I may just get someone to install another check value further up the route. I know I do have access to the upper last horizontal length but before it drops down. Do you think that would help?

What's the theory in installing a check valve right after the pump in the pit itself? I have one on the first horizontal pipe. A check valve in the pit means it has to be PVC and water proof?

Thanks.

Quote:

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Originally Posted by Milo Dolezal

DBDX18: There is a lot of sewage in that 3" discharge pipe. It weight quite a lot. You hear it when it falls down.

The "bang" noise is caused after pump shuts off and water that has been push upward the pipe now falls back on the check valve. When you attached discharge pipe to the joists you have made this noise more audible from obvious reason: pipe is touching house framing, bang produces vibration, and vibration now transfers into the joists. I would suggest you hang this pipe below the joists.

Proposed solution: I suggest that you install 2 check valves. They both should be the type with flopper inside, not spring loaded. Install one in the pit, about 6" above the pump on vertical discharge and the other one on top or the 10' riser, just before the pipe turns horizontal towards the street. I am enclosing simple drawing for better visual...

Also, make sure your transition 90s are long sweep 90s. Some loose parts, like pit cover, may contribute to the noise but are not the primary cause.

Let us know how you did......Milo

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An update...

A few weeks ago, the joint between the gate valve and the check valve splitted. Clearly, it's from the jolting when the pump shuts off.

I have another plumber come in and he worked hard to prove his theory that the discharge pipe needs to be secured so that it doesn't move. He then proceeded to tie the pipe to the joists above with steel straps and such.

No dice, the sound is as loud as when the pipe was tied down with 2x4s. However, I'm a bit relieved that it's secure enough this time that the joints/clamps don't come apart.

I've done tons of research online and this noise appears to be quite common and the few that experienced such similarly dramatic shock to the pipe, well, they don't post back to say what fixed it!

At this point, I'm left with (a) replacing the check valve, (b) turning down the gate valve to reduce water flow? And (c) installing another check valve somewhere higher.

All of which, BTW, I have doubts will work. I will however, promise to post back the solution when it does!

What ever you do, do not partially close the gate valve. I don't even think you should have gate valve on the system at all. With gate valve present, there is a great chance the noise can be generated by the valve's closing mechanism ( stem and/or gate ).

Did you install the 2 check valves as we discussed it in October ?

Also: how many bathrooms does this sewer ejector service ?

Hi Milo,

The plumbers I had taking a look at this problem advised against it for various reasons. (a) they cited that there may be an air lock problem ? (b) that the noise will increase because of the two valve flappers being hit by the water as well as being pulled by the water drained from the other end. More importantly (c) because I can't get to the vertical pipe without busting open drywall in the interior of the house and enduring the sewage aroma and mess.

I thought a shutoff valve ahead of the check valve is required ?

This ejector setup services two full baths plus the laundry.

BTW, the pump just went off and there was just a regular thud instead of the double bangs like two linebackers just jumped on the floor behind me. This is one hair tearing situation.

Some plumbers install gate valve on the discharge pipe because they want to be able to close it and then work on the pump system. However, with properly installed - and working - check valve, this gate valve is not necessary.

I would definetely check if that valve is not the source of the noise. Put your hand on the valve during discharge and feel if you can feel moving parts when pump shuts off.

There is really no need to guess on this issue. If you think our solutions based on our experience are not valid - call Zoeller engineers and they will be able to tell you right away - and w/o guessing - how to solve this problem. Here is the contact info:

Zoeller Company
3649 Cane Run Rd.
Louisville, KY 40211

Phone: 1-800-928-7867
502-778-2731
Fax: 502-774-3624
Email: [email protected]

Thanks for the contact info.

BTW Milo, I see you're in So.Cal. I would love to have someone knowledgeable own this problem and take it off my headache list. Would you know anyone with your level of expertise in this subject who may be able to take this on. I'm in Calabasas. My email is [email protected]

Thanks.

Over the years, I've had some inquiries about this problem of mine so I thought I'll come back and post the cause and solution to it. Thanks to the last email for linking back to this thread.

My problem was essentially a loose pipe joint between the pump and the elbow above the tank. Because the joint was in the tank, it took me awhile to finally find the problem. And yeah, we didn't want to mess with the innards of the tank. And of course, I was busy chasing false leads. The joint was largely submerged in the tank until of course the pump kicked in and emptied the tank. Then as the pump turned off and because there is quite a distance of piping from the pump to the street above, the back flow is significant. This joint itself is not going to decouple because of the weight of the gate, elbow and pipes above it. But the reverse water pressure after the pump stops is enough to cause the shock, shake, vibration and bang. And if I had left it unfixed for some time, may lead to further loosening issues with the setup. In my case, tightening the joint was all it took.

Good luck with your problem. Feel free to email me at [email protected] if I can help in any way.

Thanks for the update Bdbx. Always good to hear back. Your solution just might help the next guy. Tom