Back Flow Preventer?


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Old 03-14-05, 08:40 AM
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Back Flow Preventer?

Is a back flow preventer with an atmospheric port and a "reduced pressure back flow preventer" the same thing?

-Bob
Thanks.
 
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Old 03-14-05, 08:54 AM
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I have a backflow preventer with atmos vent on the piping from the cold water domestic line going into my boiler, does anybody have a picture or something of the insides of these parts? I am just trying to picture the inside of the part and how it works? I have a slow leak out of the backflow protector coming from the cold water supply line side and was wondering how the inside of these devices actually function so I can understand how the leak is happening. This is all started happening when I lost complete water in my house, and all the pressure in my pressure tank dropped.. I had to totally drain my domestic water system..
 
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Old 03-14-05, 09:24 AM
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When the water pressure on your supply side fell off it created the opportunity for the boiler water to want to back up the supply side and contaminate your domestic water. If water came out of that port, then I believe it did as exactly as it was intended to do. When this happened to me I was taught to Lift the tab on your auto fill valve (down stream a bit from the backflow preventer) and let the water run fast thru the system and that will sometimes clean the backflow valve from any bits of crud that may be there causing your leak. Also I put a hose on the system(boiler) so I did not over pressurize it. Hope this helps. Post back.
-Bob
 
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Old 03-14-05, 11:09 AM
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what do you mean let the water run fast through the system? what system are you talking about?

my question is really why water from the supply line is coming out of the backflow protector?
 
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Old 03-14-05, 01:34 PM
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Next to your backflow preventer on the downstream side is your automatic feed or "fast fill" valve for your boiler right? On this valve is a flip lever at the top of the valve. The valve is installed on your supply line at probably 12-15 psi. this maintains proper boiler water pressure for your system . If you flip that lever straight up you will feel and hear the water pressure increase that is feeding your boiler and at the same time it will flush your backflow preventer clean. I believe that the leak you see is coming from boiler water backing up to the backflow valve and not your supply as you may think. As you are "fast filling" thru the auto feed valve it will increase the water pressure at the boiler. that is why I suggest a hose or bucket to reduce the pressure back to the normal pressure at the boiler after you have "fast flushed" thru your leaky backflow preventer. It is leaking most likely because a small piece of crud from your original drop in pressure prevented the valve to not seat properly. I believe you can get more info by visiting the www.wattsvalves.com and looking at their products line and you can find the watts backflow preventer 909 with a bit of detail. sorry I make it hard to understand, that's my fault but it is really an easy fix.
 
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Old 03-14-05, 01:37 PM
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I'm assuming also that your leak is not from the connection point to your cold water supply. I'm assuming that your "leak" is from the atmospheric port part of the backflow preventer.
-Bob
 
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Old 03-14-05, 02:07 PM
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yes the leak is coming out of the piece of pipe connected to the backflow preventer vent port.

I think I do have that valve like you described with the level on the top, but I was told this valve is just to take the supply line water at 60psi and drop it down to 15psi to feed my boiler? so really this valve is called like a pressure decreasing valve or something. I do not know why I would want to force 60psi pressure past this valve directly into the boiler, this sounds like it might be a bad idea to me and it might actually hurt the boiler itself.. I do think that the water which is leaking out of the backflow preventer is indeed from the supply line water. The reason I say this is because on either side of the backflow preventer I have a shutoff level handle. If I shut off the lever on the supply line side (BEFORE) the backflow preventer then the drips get quicker almost to a steady stream for about a second or two, then the drips totally stop. So I would say the water drips are coming from the supply line side, NOT the boiler side. Besides, it doesn't make any sense how the water leak could be coming from the boiler side at 15psi instead of the supply side at 60psi.. obviously the higher water pressure on the supply side would force the boiler water INTO the boiler and not let it back up..
 
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Old 03-14-05, 02:17 PM
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by the way that valve you are talking about with the lever ontop of it, that comes AFTER the backflow preventer (ie.. this valve is CLOSER to your boiler than the backflow preventer), I think it's called a PRV (Pressure Reducing Valve)
 
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Old 03-14-05, 02:39 PM
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After the backflow TO your PRV valve is what is referred to as DOWNSTREAM from SUPPLY. So, we are both saying the same thing. Next, that is why I mentioned the hose or bucket to reduce pressure in the boiler while doing this quick fix. The "quck fill " lever used with a bucket or hose allows you to flush clean your backflow valve while not increasing the pressure in your system (boiler). The reason I found this thread most interesting is because this year I added glycol to my system to prevent freezing pipes and when I did it and shut the supply I had a backgush of boiler water come thru my backflow valve. so I went to the Depot and changed out the valve twice thinking I bought a defective part. Now I know that the original valve did it job exactly as it was supposed to. You can change the part out. It is an easy fix. Next time I will just empty an old coffee can once a week knowing that the valve is still working. But because you are able to isolate on each side of the BFP valve you are able to determine that the leak is on the supply side and I bet you would love to see a cross section of this valve. I wish I had a schematic to show you. Not long ago you had to be licensed to even buy these valves. I enjoy this post because I think we can all learn from each other. After all we are only trying to become good DIY's from one anothers advice.
-Bob
 
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Old 03-14-05, 02:49 PM
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this is my backflow preventer I have installed
http://www.wattsreg.com/products/images/hi-res/9D.jpg
 
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Old 03-14-05, 02:53 PM
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That's the same one that we all have. They cost $29.99 at the Home center. I like the way you are able to post that photo. Now THAT would really confuse the heck out of me. If you can instant message on here (maybe you can) I would like to chat about this topic of the BFP VALVE.
THANKS!
 
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Old 03-14-05, 02:58 PM
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okay couple questions..

1.) When you pull up the "Quick fill" lever on the PRV, where do you connect a hose or bucket to to collect the 60psi supply water that would normally shoot right into your boiler? I don't think my PRV has a hose outlet to connect a hose to in order to divert the high pressure water out the hose instead of into the boiler?

2.) About the backflow preventer, you mentioned that yours leaked and your replaced twice but now if it leaks again you will just keep a can under it to collect the water. Why would you not fix it? is it bad to just leave it like it is leaking? I just brought this house and I think that this thing might of had a slow leak for a long time. I never noticed a puddle because the backflow preventer vent pipe comes out the back of the furnace and I think the water drops would of evaporated or something. But if you look behind the boiler you can see on the concrete that there is all like a dirty mud build up or something, probably from water leaking out of the backflow preventer pipe... I'm not sure.. but I was told that I should replace this part if it is leaking..
The thing I don't understand though is that the backflow preventer ALREADY has 60psi going through it because the PRV is AFTER or DOWNSTREAM of the backflow preventer. So 60psi HAS to be going through the backflow preventer already, and by me pulling the quick fill lever on the PRV, I don't think this is going to do anything different inside the backflow preventer you know?
 
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Old 03-14-05, 02:59 PM
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hey check this out.. it's a cross section view of the BFP we have..
lets see if I can figure out what's going on here... lol
 
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Old 03-14-05, 03:08 PM
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You should have a gate valve at the bottom of your boiler where you can connect a hose. It should already be there ...they come with the boiler. Or else you must have copper tubing coming from your PRV that you can put a 5 gallon bucket underneath.

(2) The supply side of the BFP does not have water going thru it at 60psi until you flip the lever on your " auto feed, quick fill, or pressure reducing valve". Until you flip it you just basically a dam (like a beaver would build) at that point. When it is flipped open you will then have your 60psi gushing thru the BFP and hence flushing it out so just maybe the BFP will seat itself properly again.(inside of the brass) and stop your leak.
 
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Old 03-14-05, 03:22 PM
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http://www.wattsreg.com/pdf/ES-9DM3_M2.pdf
I have my set up just like it shows under the Boiler Installation if you scroll down

http://www.wattsreg.com/pdf/RP-IS-9D.pdf

If the BFP is BEFORE your PRV, then you HAVE to have 60psi going through your BFP at all times... cause the pressure doesn't drop until it hits the PRV... you know what I mean? because if the BFP WAS in fact acting like a dam, then NO WATER at all would be getting to the PRV, thus NO WATER would be able to get into the boiler when the boiler's pressure dropped below 15psi..
 
 

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