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Thread: Backwater Valve

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    DIY Senior Member dlarrivee's Avatar
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    Default Backwater Valve

    Is there anything wrong with installing a 3" ABS back water valve in a drain that is not below a concrete slab?



    This is the style I am speaking of, and they usually come with a sleeve and cap meant to be cut flush with the top of the slab...

    This is the 3" into 4" waste line exiting my house. The 3" line is 20" from the slab. (bottom right corner)


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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    Is there anything wrong with installing a 3" ABS back water valve in a drain that is not below a concrete slab?



    This is the style I am speaking of, and they usually come with a sleeve and cap meant to be cut flush with the top of the slab...

    This is the 3" into 4" waste line exiting my house. The 3" line is 20" from the slab. (bottom right corner)

    This is perfectly fine! In fact it's done all the time where a backwater valve is called for and the sanitary building drain leaves the building.

    I don't know about codes in the USA but in Canada there is absolutely nothing in the National Code book that says a back water valve shall be installed in the ground. In fact you're able to use them quite frequently in all sorts of places if you want to as long as you meet a few code requirements.

    Just make sure you install a back water valve that is "normally open" and you should be just fine.

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    DIY Senior Member dlarrivee's Avatar
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    Great thanks.

    I am actually located in British Columbia.

    The only thing that bugs me about this type of valve is that if it we're to become inoperable at any time you cannot replace just the flapper, you have to cut the entire thing out.

    Unfortunately most of the "serviceable" types don't seem to come in 3"?

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    Great thanks.

    I am actually located in British Columbia.

    The only thing that bugs me about this type of valve is that if it we're to become inoperable at any time you cannot replace just the flapper, you have to cut the entire thing out.

    Unfortunately most of the "serviceable" types don't seem to come in 3"?
    Hey sorry I didn't see that.

    I am in BC as well (Okanagan area). Putting a BWV there is perfectly acceptable.

    3" is some what of an "odd ball" size. There are lots of times you'll find something in 4" but not 3". Just because they sell a heck of a lot less 3". I wouldn't install 3" in a new house today. Everything would be 4" that was required to be 3".

    Don't worry too much about it acting up. Just install it and forget about it

    OR You can redo the connection to the 4" and replace a bunch of that 3" with 4" and install a 4" BWV that's serviceable. But that 4x3 wye looks pretty tight up against your foundation wall!
    Connect to the 3" with a 4x3" coupling and you'll be perfectly acceptable code wise doing this as well.

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    DIY Senior Member dlarrivee's Avatar
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    I'm located in Kelowna actually.

    The only problem with redoing a bunch of that line in 4" is that the wye that is halfway embedded in the concrete is a 4x4x3 and would need to be replaced as well... Just to much work for a certain style of valve to go in, not worth the effort.

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    I'm located in Kelowna actually.

    The only problem with redoing a bunch of that line in 4" is that the wye that is halfway embedded in the concrete is a 4x4x3 and would need to be replaced as well... Just to much work for a certain style of valve to go in, not worth the effort.
    Penticton here. I would agree with you and just go with a 3" valve!

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    DIY Senior Member dlarrivee's Avatar
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    Also, is there a certain distance that a backwater valve must be away from any drain branch into the waste line?



    I want to move the washer and dryer this corner as well, but I'll need to add a new drain for the washing machine...

    Can I have a wye right beside the backwater valve?

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    Moderator & Master Plumber hj's Avatar
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    Default Bwv

    The question is not whether it is okay to use it or not, the real question is WHY would you do it. Unless you have some situation not shown in the picture, you have an "overhead" sewer, and as such there is nowhere for the water to overflow into the basement. An overhead sewer will continue to operate normally, even during a main sewer backed up condition, BUT if you install a backwater valve in it, THAT will prevent you from using ANY water in the building during a main backup condition.

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    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by hj View Post
    The question is not whether it is okay to use it or not, the real question is WHY would you do it. Unless you have some situation not shown in the picture, you have an "overhead" sewer, and as such there is nowhere for the water to overflow into the basement. An overhead sewer will continue to operate normally, even during a main sewer backed up condition, BUT if you install a backwater valve in it, THAT will prevent you from using ANY water in the building during a main backup condition.
    I have a sewer ejector pump located below the slab for the basement bathroom, there's a trap and stand pipe for the washing machine in the basement as well.

    It looks like it's damn near impossible to find a normally open 3" anyways...

    Should I be looking at just installing one between the ejector pump and the main drain, I believe it's 2" abs... I could use a normally closed valve in this situation and not damage it, if the lines ever needed to be snaked...
    Last edited by dlarrivee; 11-15-2009 at 09:22 AM.

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    I have a sewer ejector pump located below the slab for the basement bathroom, there's a trap and stand pipe for the washing machine in the basement as well.

    It looks like it's damn near impossible to find a normally open 3" anyways...

    Should I be looking at just installing one between the ejector pump and the main drain, I believe it's 2" abs... I could use a normally closed valve in this situation and not damage it, if the lines ever needed to be snaked...
    Your ejector pump by code should already have a check valve installed on the outlet of the pump. I'm sure it does if you don't notice your pump cycling on and off every 10 seconds :P

    A backwater valve when you're below grade is never a bad idea! If your street's main ever backs up guess where that sewage is gonna go? To the lowest point and your house is one of those low points.

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    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by Doherty Plumbing View Post
    Your ejector pump by code should already have a check valve installed on the outlet of the pump. I'm sure it does if you don't notice your pump cycling on and off every 10 seconds :P

    A backwater valve when you're below grade is never a bad idea! If your street's main ever backs up guess where that sewage is gonna go? To the lowest point and your house is one of those low points.
    If it does indeed have a proper check valve on it, it must be hiding or integrated into the pump itself.

    Doherty, you mentioned I should make sure I use a normally open style, I don't see anything available in 3" that's normally open..?

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    If it does indeed have a proper check valve on it, it must be hiding or integrated into the pump itself.

    Doherty, you mentioned I should make sure I use a normally open style, I don't see anything available in 3" that's normally open..?
    By code any backwater valve you install must be of the normally open kind.

    You don't see anything coming out of your sump that looks like it could be a check valve? In these parts we usually use a white pvc compression style check. If you don't have one you should look at installing one....

    I can check with my local wholesaler in town here and see if I can find a 3" normally open valve. If I can get ahold of one I can always buy it for you and ship it to you. It'll cost you a bit extra but then atleast you'll have the right part.

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    DIY Senior Member dlarrivee's Avatar
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    The only normally open one that I have found is the big mainline style with the clear top...

    I'll have to investigate further the lack of check valve, is it possible that it has been installed below the lid of the tank?

  14. #14
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    The only normally open one that I have found is the big mainline style with the clear top...

    I'll have to investigate further the lack of check valve, is it possible that it has been installed below the lid of the tank?
    Yes very possible. I am sure you have. You can test yourself by simply having the pump kick in and let it run till it pumps the sump dry. You shouldn't hear much water draining back into the tank once the pump kicks off. You will hear a bit (the water between the pump and check valve). If you have no check valve you'll more then likely hear a decent amount going back into the sump because you will get the water from the pump to highest vertical portion of the piping (before it starts grading down horizontally) draining back into the sump.

    If you try this and you can't tell or are unsure just pop the top of the sump off and take a picture!

  15. #15
    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by Doherty Plumbing View Post
    Yes very possible. I am sure you have. You can test yourself by simply having the pump kick in and let it run till it pumps the sump dry. You shouldn't hear much water draining back into the tank once the pump kicks off. You will hear a bit (the water between the pump and check valve). If you have no check valve you'll more then likely hear a decent amount going back into the sump because you will get the water from the pump to highest vertical portion of the piping (before it starts grading down horizontally) draining back into the sump.

    If you try this and you can't tell or are unsure just pop the top of the sump off and take a picture!
    It's not looking good in the check valve department...



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