DWV Backwater Valve

Users who are viewing this thread

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
We have the kind where the door is closed, and the flow of water *opens* the door. It's all CI - suppose code regulations.

I've seen the plastic ones - which might seem like it's a more superior design ?

I know it's not foolproof - I am mindful around late Aug/Sept to remove the cover and just to make sure nothing (is blocking) the door

Sewer systems just can't handle heavy rainloads or flash floods. Last time I recall was during Hurricane Irene:Sandy.

On this recent rainy event, every house or the mass majority on the block got overflow...
I've walked by some houses with trash bags, one has a hose running out through a window , etc.

Here'in lies the question. While I did get minor -backflow- , the door did hold the water from back flowing , I get that the door is not *100* sealed when it is closed and in thinking as such, I suppose the backflow water - pressure as the DMW backs up and fills up the pipe volume s what really (presses the door tight) to seal it.

For those familiar with these types of things, is what I am describing accurate, The door is not *sealed* enough to stop even minimal backflow and it does take *awhile* for the *pressure* of the full DWV backup up to seal the door -pressurewise*. The tub got filled up about 3/4 way full and just a small trace of water back flowed out of the bottom of the toilet ( 2 old t shirts was sufficient enough to soak this up)
 

Sylvan

Still learning
Messages
2,763
Reaction score
692
Points
113
Location
New York
The "Door" is supposed to be open slightly open to allow for sewer gases to escape.
 

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
Ah, I see. Then I guess my -best education- on how it works sounds about right. If there is backflow, there may:will be some making it past the door until the door get's fully shut. Fully shut occurs when the -DWV backflow- fills up to the volume point that the water volume pressure is great enough to -press- the door in place, creating a *greater seal*.
 
Last edited:

Tuttles Revenge

In the Trades
Messages
4,169
Reaction score
1,439
Points
113
I think there are a few designs for BWV that better than others. Some have flappers that swing on a hinge, while others are swinging on their own rubber similar to a toilet flapper that attaches to the overflow. We install them a lot in Seattle after a 2006 flood event where several people died in their basements from flooding sewers.

In some instances we install the typical BWV that hangs down and is normally closed, those are for properties where we are separating a flood prone floor from the floor above that ties in downstream, or if it blocks the air flow, then we have to tie in a vent from downstream and connect it above the height of the next upstream manhole cover.

In a lot of cases we install BWV that are normally open and the gate floats up to close. These are for properties where all of the floor levels are below the next upstream manhole cover. They allow the air to flow through normally.

I personally don't live with one installed so I don't know if they allow a bit of back flow, but you're a few steps ahead of most in not only having one installed, but inspecting it on a regular basis. have you ever had to clean it?
 

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
We had some work eon's ago and one of the contractors must have done a #2.......
When we got backflow and it failed, I suspect it was the contractor....as there was a large lump of #### right on the lip of the door after post event and checking why the door did not do it's job.

Aside from that, no one in our household has hard lumps AFAIK ;-)
But I have a very Large Apron Sink that is close so what I will do if the weather is calling for flash: heavy or just long extended rains is a little insurance. I fill up the Apron sinkand let it drain. It's got some Volume to it,

Do that 3-4 times just to let the inrush of the water (which is fairly close to the main trap) in theory, flush the door.

I suppose the door must have worked in this recent event - last major water was about 2 years ago....and alot of houses along the block got ingress. To the point where stuff being tossed, etc. While I got some, it was so minor....2 old t shirts soaked whatever came from the toilet, and while the tub did backup to about 2/3 full, it drained whenever the pressure was relieved and the door opened.

I mean in an ideal world, I would get zero backflow....but I now understand more of the *door* as I observe what I observe in water backflow that it has allowed in.
 
Last edited:

Tuttles Revenge

In the Trades
Messages
4,169
Reaction score
1,439
Points
113
I've never seen or even installed a cast iron BWV either. Would be interesting to see how they differ. Ours are either ABS or PVC and easily maintainable... errr.. At least I install them to be easily maintainable.. I never have to do that after we're done with the project.
 

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
I've never seen or even installed a cast iron BWV either. Would be interesting to see how they differ. Ours are either ABS or PVC and easily maintainable... errr.. At least I install them to be easily maintainable.. I never have to do that after we're done with the project.
I think it's more a local code thing....It's just a big ole cast unit with a brass door on it.

Akin to how Romex was not allowed for quite some time until the last decade or so where it was allowed for use in 3 family unit and below....etc. I may be way off on Code but it's something to that effect.

I would think a *plastic* door of any kind would be better since there is reduced weight - whether it be a door that is always close or always open
 
Last edited:

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
I personally don't live with one installed so I don't know if they allow a bit of back flow, but you're a few steps ahead of most in not only having one installed, but inspecting it on a regular basis. have you ever had to clean it?


Off topic or on topic. But I wonder, in the realm of things, when pros install these - do they ever *see* the benefits:results of the work or it's simply just an install. And or we install this cause it is better on paper, or we install this because we service X yearly, and this one seems to work better than X one...Granted you might have to revisit it if one needs it serviced ?

There was another BW valve that was much more beastlier ......when I was looking at these things. It was based off a float mechanism but the door was a knife edge style that went down as it shut. I suppose this design also was meant to -cut--sever-- if something:anything that would be impeding in that opening.
 

Jeff H Young

In the Trades
Messages
8,870
Reaction score
2,211
Points
113
Location
92346
If you think you need to change backwater valves . Id change it too , I dont know your code Ill leave that to you to find a code legal replacement for your area .
 

John Gayewski

In the Trades
Messages
4,343
Reaction score
1,338
Points
113
Location
Iowa
I don't think backwater valves are very effective. First of all every time I open one to inspect it, literally every time, there is either a turd or toilet paper sitting under the flapper. Second of all there's no alarm or indication that it's in a backwater position, unless you feel like checking it manually every time you flush your toilet or empty your bathtub. "honey I'm taking a bath." "did you check the backwater valve dear?" Third every time we install one, the very first reason event inevitably happens and the homeowner calls to say their basement got water in it. Not as much as last time, usually, but if we are installing mechanical devices in sewer systems they should work.
 

Tuttles Revenge

In the Trades
Messages
4,169
Reaction score
1,439
Points
113
Off topic or on topic. But I wonder, in the realm of things, when pros install these - do they ever *see* the benefits:results of the work or it's simply just an install. And or we install this cause it is better on paper, or we install this because we service X yearly, and this one seems to work better than X one...Granted you might have to revisit it if one needs it serviced ?

There was another BW valve that was much more beastlier ......when I was looking at these things. It was based off a float mechanism but the door was a knife edge style that went down as it shut. I suppose this design also was meant to -cut--sever-- if something:anything that would be impeding in that opening.

The floating knife BWV is made by SMITH I believe. I had a customer request one after their BWV failed and their home was flooded. However, it requires 9 inches of water/waste to rise up in the system before the float activates and in their home, that would be already flooded so they went a different route that involved suing the city who had originally installed the BWV in their sewer line. When I briefly was researching that unit my wholesale cost was over $1500.

I don't think backwater valves are very effective. First of all every time I open one to inspect it, literally every time, there is either a turd or toilet paper sitting under the flapper. Second of all there's no alarm or indication that it's in a backwater position, unless you feel like checking it manually every time you flush your toilet or empty your bathtub. "honey I'm taking a bath." "did you check the backwater valve dear?" Third every time we install one, the very first reason event inevitably happens and the homeowner calls to say their basement got water in it. Not as much as last time, usually, but if we are installing mechanical devices in sewer systems they should work.
The Mainline BWV does have an alarm option. However its a big unit.
 

Reach4

Well-Known Member
Messages
38,846
Reaction score
4,427
Points
113
Location
IL
I don't think backwater valves are very effective. First of all every time I open one to inspect it, literally every time, there is either a turd or toilet paper sitting under the flapper.
That is the concern with the common flapper "normally closed" valve. The classic debris was a mop string, but I think string mops are seldom used today.

The normally open valve does not have that problem, or at least to that degree. http://backwatervalve.com/products/fullport-backwater-valve.html A downside for retrofits is that there is a required drop between input and output.

A system that can use use either is to have sewage flow to a pit that is normally gravity drained to the sewer. If the sewer water rises, an ejector pump ejects sewage into the street side of the backwater valve. A bit of leakage is overcome by the pump. If the pit is big enough, there is some storage that could help ride out a power failure. https://www.floodexperts.com/ If we were to imagine a perfectly-sealing backwater valve that services a whole house, you would still have to discontinue water usage during the event.

The gold standard against basement sewer backup flooding is called "overhead sewers". Basement waste all goes a pit, and that waste gets pumped up high, to join the gravity-moved waste of the higher floors.
 

Jeff H Young

In the Trades
Messages
8,870
Reaction score
2,211
Points
113
Location
92346
I agree they do get fouled but code requires a back water valve. 23 years mine never has been inspected .
I come from the world of new construction where a backwater valve is installed for 2 reasons only. 1 Its code 2 because it was specificaly called for on documents.
Ive installed many over the years but on new homes the original plumbers dont get involved much after warranty .
Ive seldom installed B/W valve where code didnt require . and when I did It was not a ton of research or callbacks just a preventitive measure
 

Reach4

Well-Known Member
Messages
38,846
Reaction score
4,427
Points
113
Location
IL
Your world probably does not have a lot of basements that feed into sewers that somehow get overloaded during big rains.
 

Jeff H Young

In the Trades
Messages
8,870
Reaction score
2,211
Points
113
Location
92346
Your world probably does not have a lot of basements that feed into sewers that somehow get overloaded during big rains.
No we dont have that much of that . im sure there are areas in my state where its a problem but no where near as bad as older cities in the east.
 

Chefwong

Member
Messages
949
Reaction score
11
Points
18
Location
District of Columbia
Of course, the internet tracking cookies and all that....
A video popped up on my feed. The CI unit I have, the demo showed it flipped on its side (door closed). Water was poured on the fitting end and *some water* was seen coming out the other end. So even as such, it's not a complete seal.

Not in a rush, but going to probably figure out a different unit to replace.
It is invasive ......if not expensive on a round #2 of this. Breaking up the floor, etc....

Had I not stumbled upon this video, it would not have pushed me to re-consider something that is a more tight fitting seal...

It's literally a *sh1##y* situation when you do have backup. The 1st time we got it, I swore I would never want to be in that situation again.....


Luckily in this instance, like I said, 2 old t shirts thrown around the base of the toilet was enough to soak the small amount that came out. I know it was *alot more* as the tub was 2/3 filled....

Same zonings have allowed old buildings/housings to be torn and a 1-2 more stories added .....
So more density with zero change in the upgrades to the city sewer itself.
It can only be the same or worse as far as backup unless the sewer lines in itself are overhauled...
 
Last edited:

Sylvan

Still learning
Messages
2,763
Reaction score
692
Points
113
Location
New York
th



Cast iron back water valve, I like Josam or JR Smith
th


Some cheaters :) install a BWV and install a wye AFTER the house trap and also after the back water valve and install a sewer ejector so if the valve is secured the waste empties into a pit properly vented and it forces the waste to the city mains.

Just make sure the check valve is working to prevent sewer waste from entering the structure
 

Reach4

Well-Known Member
Messages
38,846
Reaction score
4,427
Points
113
Location
IL
Some cheaters :) install a BWV and install a wye AFTER the house trap and also after the back water valve and install a sewer ejector so if the valve is secured the waste empties into a pit properly vented and it forces the waste to the city mains.
That is the basis of the system that I posted the second link to, in #12. That always surprised me that sewer systems would allow pumps to pump pressure into a sewer. It may be that only some sewer systems allow that.
 

Jeff H Young

In the Trades
Messages
8,870
Reaction score
2,211
Points
113
Location
92346
That is the basis of the system that I posted the second link to, in #12. That always surprised me that sewer systems would allow pumps to pump pressure into a sewer. It may be that only some sewer systems allow that.
I dont think code allows pumping waste when a gravity is possible , practicle, and not some hardship to install.
Thats what I dont understand about a overhead sewer system isnt it illegal to install one just because you want to pump your waste into the neighbors house? We can only pump when grvavity wont work
 

Reach4

Well-Known Member
Messages
38,846
Reaction score
4,427
Points
113
Location
IL
An overhead sewer for the upper floors is pretty much equivalent to what happens with no basement. If you retrofit to overhead sewer, you stop using the pipe that was going to the sewer to go to the sewer. Instead you feed a vented sealed pit. That pit gets pumped.

In some areas, new construction with basements are required to put in overhead sewers. There are often programs run by the municipality, but maybe funded by a federal grant. It is cheaper than a town redoing the sewer system.

Some places still have combined sewers.

With land values in much of California high, I would expect basements to become a lot more popular.
 
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