Drain line shakes -- do I need another vent?

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Old 08-28-11, 06:12 PM
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Drain line shakes -- do I need another vent?

I just installed a new, long 2" PVC drain line that hooks to my 4" line below the one bathroom in the house. This is a 63' run of 2" PVC as it's coming from my garage via a sewer ejector pump basin outside. When the pump runs, it seems to push the water ok but when the pump shuts off (thereby closing the check valve outside) the entire 2" pipe shakes violently for about ten seconds, creating quite a noise.

I thought this new 2" line would be using the vent from the bathroom but maybe it needs its own vent? If so, where in the 63' run would I put it? Or, could the shaking be caused by something else?
 
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Old 08-28-11, 06:19 PM
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Hi,

So you put a bath in the garage?

The ejector is vented properly? Is the pipe pitched properly?

You probably need a additional check valve. Its not the vent.

Mike NJ
 
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Old 08-28-11, 06:44 PM
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The garage is now a little guest house and it all drains into a 5' deep sewage basin buried just outside the garage which uses a Zoeller N267 1/2 HP pump that exits into the 2" line. That 2" line has a Zoeller cast iron check valve located two feet after the pipe leaves the basin. The 2" line then runs 30' (with a slight downhill slope), enters the basement foundation wall, goes uphill about 4', runs about 30 more feet horizontally with a few elbows until it enters the 4" main.

The ejector basin has a vent line of its own that goes back into the garage wall and through the garage roof.
 
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Old 08-28-11, 10:37 PM
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When was this installed? Did a contractor do the work?

I have to look into the code and or the specs for that pump. After the first drop from vertical I dont think it can go vertical again with that kind of distance also. Too much head pressure.

Off the top of my head a check valve would be needed where the pipe goes up the 4 ft.

Is the pipe pitched the 30 ft past that 4 ft section?

Mike NJ
 
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Old 08-28-11, 10:46 PM
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A couple of licensed contractors installed it recently (with my help) and it already passed inspection from the local jurisdiction. It hasn't been used yet other than testing with water. I was told during the design phase (Zoeller helped me and a Zoeller distributor did as well) that it didn't matter if the pipe was sloped or not after it leaves the pump and that it didn't matter if the pipe was empty or not after the pump shuts off as the next cycle would clear it out.

After that 4' vertical rise, the pipe is mostly horizontal for the last 30 feet.

Zoeller told me that this pump is their smallest cast-iron unit and that it is somewhat too powerful for the tiny rise that I need but it would work-----my garage is only a few feet lower than the house. That's why they suggested I use such a deep basin ----to get the pump to work a bit more.
 
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Old 08-29-11, 06:17 AM
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Usually the bang is from the water coming back after the pump has stopped. It hits the check valve and bang!!!!.

I would think a run that long, plus being more vertical at places, additional check valves are needed.

I am thinking before or after that 4' section. I would say put one before.

Zoeller did not specify a check valve every so many ft for such a long run???

Mike NJ
 
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Old 08-29-11, 08:12 AM
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Thanks Mike. No, Zoeller didn't mention anything about two check valves---neither did the distributor. Why is it you don't think venting is the reason for the shaking? I was going to try adding one of those air-admittance valves (Studor brand) somewhere along the 63' run but you don't think that would help?
 
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Old 08-29-11, 11:09 AM
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Confirm when the pipe shakes?

Its when the pump kicks off? Seconds after?

Its the surge of waste goining backward and hitting the check valve. If you add another check valve it will lessen how much water hits the first one.

Heck might need 3 of them or more.

I think there is some document that shows to put them every 25 ft for long runs. Cant be sure though.

Mike NJ
 
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Old 08-29-11, 11:14 AM
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The vibration is immediately after I unplug the pump. It shakes the entire last 30' of 2" PVC (the first 30' is buried outside) for about ten seconds. Several loud thumps every second or so during that ten seconds.

Why don't I need a vent on that line?
 
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Old 08-29-11, 11:22 AM
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The thumps is the water going back and forth in the pipe.

Tell you what. If you remove the check valve you have I bet it goes away.

Why don't I need a vent on that line?
Venting is so water is not siphoned from traps. It really has no affect on flow. I know alot of people dont believe it but water will flow without vents.

You could try your studer vent and prove me wrong, but I am 99% sure it will not work. It may lessen the affect because it may act like a water hammer device, but I am not thinkg so.

Mike NJ
 
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Old 08-29-11, 11:30 AM
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AAVs will only function under negative pressure situations they are not suitable for all venting applications, such as venting a sump, where positive pressures are created

Your pit creates positive pressures.

Mike NJ
 
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Old 08-30-11, 09:04 AM
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Yesterday, I again talked to the guy who helped me design the system and told him about the pipes shaking after the pump turns off. He said the design is fine and he agreed that I do not need any venting in the 63' run. He said the main problem with my installation is that the plumber didn't brace the 2" ABS piping enough---he recommended using 2x6's every 30 inches and clamping the 2" ABS onto them. He said the shaking is to be expected with such a strong pressure. He did think it makes better sense to connect the 2" into the 4" further away from the house toilet though---I currently have it connected just a foot away from where the toilet hooks into the 4". He said I don't need another backflow and he only uses more than one if he has an extra long run of 300 feet or more. Interestingly, he said pump lines rarely clog up as the pump force jets out the line each time it runs.
 
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Old 08-30-11, 11:22 AM
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As long as you tied into the 4" after the toilet vent for the toilet you are descibing. If you hooked up before the vent you may get siphoning from the toilet.

Yes secure the pipe. If its just flapping in the wind of course it will shack, rattle, and roll.

I would bet even after securing you still get the bang.

Hey since you mentions the toilet you must be getting a burp in that toilet, correct?

Mike NJ
 
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Old 08-30-11, 11:27 AM
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The only thing I've noticed in the toilet is a slight movement of the water in the bowl while the pump is running. I've only tested it three times now so haven't watched the toilet bowl when the pump turns off.

Yes, the 2" line enters the 4" line after the toilet, not before. But still, it's only a foot away so I think I'll punch a hole in the foundation wall and run the 2" further out into the yard and connect to the 4" out there instead. I would sleep better at night.
 
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Old 08-30-11, 11:39 AM
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Is the a vent for that toilet where you tied your line into? There should be a 3x2 Y somewhere.

Did the plumber drill a weep hole below the check valve?

I believe I read you have a cast iron check valve?

This should be replaced with the silent type that are spring loaded and close slowly.

Sewage Check Valves

He probably oversized you pump IMO.

Mike NJ
 
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Old 09-01-11, 01:25 PM
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Yes, there is a vent and there is a 3/16" hole in the pipe leaving the pump, as Zoeller recommends. I'll look into that other check valve you recommend.

I decided to disconnect what's been done where it connects to the 4" main and reconnect it out in the yard, much further away from the house toilet. I'm doing it myself this time as I wasted my money with the plumber as I have to remove all his ABS that was installed poorly. I should have done it myself the first time.

Thanks lawrosa for your suggestions.
 
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