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Plumbing vault in concrete floor

Posted by arigger (My Page) on
Wed, Feb 12, 14 at 11:59

Hi all,
I'm about a year and a half into a mid-century, two story ranch home. It's been really great having this forum as a resource.
In this episode, I'm replacing some very well worn 1979 red shag carpet in the basement, and laying down a floating laminate floor.
I discovered a plumbing vault in the concrete floor, and after some research, learned that it's for a backflow valve that has a manual gate as an emergency feature in the event of a long-term backflow event. However unlikely that may be. This valve was installed after the fact [1976], so the masonry work leaves something to be desired.
My question starts with, what should I be considering when I cover this thing up?
The vault was lined with aluminum foil... is that a thing? Should I replace that? My current plan is to line it with plastic, to protect the valve and it's parts, and use some expanding foam to fill the voids around the vault cover. Should I then do away with the plastic liner, or keep it as a moisture barrier thingy?
Then, once I've leveled the vault cap and prepped it to lay floor over... How easy should I try to make accessing that valve? I assume that if I were to have such a serious backflow event, that floor would be toast in any case, so it's not the end of the world if I had to tear it up to get at the valve, but perhaps some consideration needs be made. At least so's I don't forget that the thing is even there. 'Cause I will. I'll bet the last owner never even knew it was there in the first place.

Thanks for being there. And if you're interested, I'll be posting in a couple weeks about my experience with that "dimple-mat" product called Delta-FL.

Follow-Up Postings:

RE: Plumbing vault in concrete floor

I'm surmising that this closes the main sewer to prevent a back-up into your basement. Someone must have experienced a problem to have invested in a shut-off. It couldn't have been cheap. The problem is you have to be home to manually close the valve and that sort of defeats things.

I would speak with a reputable plumber about installing a check valve that would prevent a sewer back flow. Many years ago we owned an old house where we had problems and solved them with a lift station. Such a backflow check-valve was part of that installation. It did require periodic preventative maintenance so access (in your case) would be necessary.

Hope this helps.

RE: Plumbing vault in concrete floor

From what I can tell, this device is both an automatic check-valve, AND a manual shut off. The theory being that a check-valve works for sudden surges, but isn't suitable for flooding of any duration. Thus the manual gate valve.
[From the manufacturer]: "Functions as a drainage control valve; flapper type backwater valve provides temporary protection against sewage backflow surges. Manually closed "spade" type gate valve provides additional complete "closure" protection during emergency conditions, when building is completely shut down or during extended periods of backflow conditions."
And yeah, it must've cost a fortune. So much so that they chose not to hire a decent mason to finish the hole nicely.

RE: Plumbing vault in concrete floor

I'm no expert on these things. But I am Type A and I would want to know that an old piece of hardware can still be counted upon in time of need before I invested $$$'s into a basement floor. Maybe your municipality has improved the sewer system in the past 40 years eliminating the original problem.

I thought I was safe but a so-called 100 year storm put 3 feet of water in my basement. Lost furnace, laundry and a refrigerator plus furniture and a lot of clean-up. Insurance didn't cover a dime. That's when I installed a fail-safe system. More than 20 years later the family who bought the place was flooded because they didn't maintain what was there.

RE: Plumbing vault in concrete floor

Excellent point. Looking through the manufacturer's information sheet I see that this thing should get semi-annual maintenance. I can guarantee the previous owners had no idea it was even there.
Looks like I'll be planning/ designing an access hatch after all.
I have no fear that this thing will ever go to work, but what an awful thought... backflow.
Now to decide wether to hire a pro to do the cleaning... or do it myself. Sounds messy.

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