Backflow preventer sizes?


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Old 09-19-05, 07:49 AM
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Backflow preventer sizes?

Hi,

A few months ago we had a sewage draining guy in to flush our basement drain as some foul-smelling water was occasionally rising up over the surface of the basement floor. At that time, he had mentioned that I should install a backflow preventer in the drain to prevent possible damage to the basement. This seemed like a good idea so I picked one up to match the drainage hole. A 3" preventer was too large (wouldn't even fit the hole) and a 2" one was too small (almost dropped it in the hole!) - sound a bit like Goldielocks? The backflow preventers everywhere seem to be 2", 3", or 4" yet our drain appears to be 2 1/2". Is this possible (I'm in Ontario, Canada)?? Am I missing something obvious here? Should I be looking for a plumbing specialty store? Any help would be appreciated - this one's been on my to-do list for quite a while...

Thanks,
Steve
 
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Old 09-19-05, 09:55 AM
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Back water valve.

Parkers: My first question is where are you attempting to install the back water valve? It sounds like you are trying to place it into a floor drain. It needs to be installed either on the building drain or just as the line exits on the building sewer. Please post back with a little more info and we will help you work through this.
 
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Old 09-19-05, 10:07 AM
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wrmiii: Yes, I'm trying to install it in the basement floor drain (as per the recommendation of the guy that was flushing the pipes). This is where he said it should be but seeing as how none of them fit, perhaps he was wrong...

Just to make sure we're talking about the same thing, it's the rubber/brass fitting that you lower into the drainage hole and then tighten the screw to expand the rubber seal, correct?

P.S. forgive my ignorance
 
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Old 09-19-05, 02:28 PM
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Floor drain

Parkers: Not even close. What you are describing is called an expansion plug. This is more generally used in the automotive trades. If you happen to find one that would seal off the drain it would render this floor drain useless. The thing you would want to consider is why it is backing up in the first place, and remedy the problem. If it were due to overloading the drain system because of an improperly sized drain, then there would be very little back pressure on this portion of the system and a floor drain with a built in backwater valve would be sufficient. This is a floor drain and P-Trap combined with basically a ball that sits in the bottom. Water can run through the drain but if it were to try and back up the ball floats to the top and seals the drain. Installing this would involve breaking out the floor around the existing drain and installing the new one.
I hope we are on the same page now. I think this is something you could do as a home owner. If you need more advice or guidance just post back.
 
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Old 09-19-05, 04:15 PM
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Backflow valve is totally different from a back water valve.

If you have a floor drain that occassionally has water back up around that area when you are having rain events, there is a little gizmo made to stop that.

You need to look at the floor drain when it has water in it at it's normal elevation in the trap. If there are threads in the 2" hole, you can buy the adapter that screws down into the drain with a ping pong type ball. They are about $4 for the plastic model and $12 for the brass one.

If there are no threads, things just got more complicated. You have the option of threading the cast iron with a 2" tap or just replace the floor drain with a new one that has the threads. This envolves breaking concrete and having plumbing fun.

Good luck with your project, more questions ask and someone will answer you.
 
 

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