BackWater Valve Working - Explain the Technical Observation

Users who are viewing this thread

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
We're getting Some Flash Heavy Rain Flooding.

I know the BackWater Valve is working I think ?
The lowest point in the hose and about 20 feet away is a toilet tank.

Water is being siphoned from the toilet for whatever reason. Is it due to potential water *inside* the house and once the water pressure was let off and the door -opened-, it also siphoned out the water from the bowl of the toilet ?
 
Last edited:

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
No observation of rising water.

But something occured in the toilet bowl closest to the main. A suction of some sort that actually siphoned water from the bowl !

The only thing I could think of is the BW valve door being closed and when the pressure was relieved and the act of the door opening/water pressure also draining instead of backing up, it created a suction strong enough to siphon water from the bowl.
 

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
Granted todays toilets use so little water. The water level in the bowl was not dramatic - like nothing in the bowl, but it was definitely noticable that it was lower in the bowl. Almost to the low point of the outlet/trap.

The only reason I can see water siphon from the toilet was due to some suction cavitation (if cavitation is in the realm of plumbing terminology)

Years ago, with Irene, before backflow install, water was coming up from said toilet. It was not pleasant. It was costly, but we had the backflow installed. Did not even want to deal with that mess ever again .Hence, it was on my radar to see if we got any with large rain events

Eh, can't complain. Haven't checked with the neighbors but no backup water this time around.
 
Last edited:

John Gayewski

In the Trades
Messages
4,324
Reaction score
1,319
Points
113
Location
Iowa
It is possible that strong winds and rain could effect your vents through the roof, this could cause some of this.
 

hj

Master Plumber
Messages
33,602
Reaction score
1,040
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
IF the water backed up in the pipe until it was just under the toilet, when the backwater valve opened to allowing the water to drain out it would have sip;honed the water out of the bowl. If this happened, the BWV was NOT working.
 

Reach4

Well-Known Member
Messages
38,797
Reaction score
4,412
Points
113
Location
IL
Close the lid of the toilet to keep the dog from drinking there.:p

But really, it would seem to be something quirky with the venting.
 

Jeff H Young

In the Trades
Messages
8,759
Reaction score
2,166
Points
113
Location
92346
AS HJ said if water rises in the system backflow valve isn't doing its job unless its shut due to back up of sewer and you unknowingly continue to use plumbing inside home causing rising water, eventually water drains causing suction. Its rarely a vent issue (though extreme wind I suppose could)
 

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
Not that it was on my radar, but post#6 , John raises a point I never considered which was maybe some ingress of water from the vent.

Some by-product of inside water usage was on my radar. In times where I believe backup may occur, we make it a point to minimize usage internally as such already. Nothing was coming out from the toilet....which I knew was the low point of (if the bw valve was not working), all sorts of goodness would have slowly or fastly spewing out.

All good I suppose. No backwater and everything is bone dry.

For clarity on the suction, from a plumbing standpoint.
Are we saying it would have have occured if the line was empty and it was -free air suction- from the door of the BW opening.

And the suction would only have occured if there was liquid (inside) behind the backflow leading up or close to the toilet stack, that when the door -opened-, it created a suction of the toilet bowl.

AKA, the suction I thought (which was free air) is nil-impossible ?
 
Last edited:

Jeff H Young

In the Trades
Messages
8,759
Reaction score
2,166
Points
113
Location
92346
if the drainage system gets filled with water above the vent take off on the w/c and then drops the water will get "sucked" out of toilet
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks