backflow preventer on boiler feed

[pybyr]

Hello all--

OK, assume that you're in a situation like mine where I am free to do my own work with no permit, no inspection, no code.

Assume also that I try to do things as well as possible, and indeed lean towards overkill in design and construction-- but that I prefer to stay away from additional complexity with no particular benefit

I know that many codes require a "backflow preventer" on a boiler feed, just to be sure that water and contaminants from the boiler could never flow backwards into potable water, especially when connected to a public water system.

I get that backflow prevention makes sense there, especially because no one knows what's in someone else's system.

I've got my own stand alone domestic water system (supplied by a great old spring), and will be running plain water in my boiler.

a boiler feed with a backflow preventer will cost me about twice what a regular boiler feed regulator will

would I be shortsighted to omit the backflow preventer?

thanks!

 

[Nofossil]

Hello all--

OK, assume that you're in a situation like mine where I am free to do my own work with no permit, no inspection, no code.

Assume also that I try to do things as well as possible, and indeed lean towards overkill in design and construction-- but that I prefer to stay away from additional complexity with no particular benefit

I know that many codes require a "backflow preventer" on a boiler feed, just to be sure that water and contaminants from the boiler could never flow backwards into potable water, especially when connected to a public water system.

I get that backflow prevention makes sense there, especially because no one knows what's in someone else's system.

I've got my own stand alone domestic water system (supplied by a great old spring), and will be running plain water in my boiler.

a boiler feed with a backflow preventer will cost me about twice what a regular boiler feed regulator will

would I be shortsighted to omit the backflow preventer?

thanks!

My $0.02:

I've never had a backflow preventer in my life that did not leak. I always end up using a shutoff valve to isolate the boiler from the house water. That means I could have a failure that would result in loss of water pressure for the boiler system - seems like an acceptable risk, and I'd know if I had a leak.

The safety concern is that if water pressure in your house dropped below boiler pressure, water from the boiler could flow backwards into the house system and you might never know it happened. Realistically, I suspect that a spring loaded check valve would be fine.

I also like the semi-closed system with an open-topped expansion tank in the attic. Such a tank could be kept at a minimum fill level with a toilet tank type valve, and that would also ensure no chance of back flow.

 

[Tony H]

We used a seperate check valve type back flow preventer the type used with well pumps. I think it was 12.00 and well worth it to ensure boiler water could not get back in the well water. We also used 2 ball valves to isolate the regulator and check valve for replacement or shut off if needed.

 

[pybyr]

thanks guys--

at least in the initial phase of this project, all of my hydronics are going to be in the cellar, so I won't need much pressure at all to keep anything working upstairs or on a second floor, so I will probably run my boiler pressure relatively low-- from what I've read (sigenthaler's book, etc), you can deplete the oxygen from the water faster and further at low PSI than high PSI.

So risk of the boiler being above the domestic system's water pressure will be lower in my system than most.

Spring loaded check valve, without the side drain like the official anti-backflow, sounds like a great idea. that (a basic check valve) is all I use to make sure that the overflow line from my spring (which I sometimes use to water the garden) never lets guck siphon backwards into my domestic water reservoir

thanks again

 

[Vtgent49]

I'm north of Waterbury. I was told my 25 year old wood/oil boiler now needs a backflow preventer even though it was ok for 25 years, or else the local heater guy couldn't work on our system to clean/adjust the oil portion (which consumes about 100 gals/year). So, I put one in. It's overflow does dribble into an old coffee can, even though brand new. It has a pressure reducer also.

I do leave mine "connected", meaning pos pressure to the boiler all the time. And my old boiler water does get "stinky" except that I often drain/refresh it due to making system changes. So, a backflow to my well water system might be unpleasant. If you went all the way to a glycol system, then it does make sense. Otherwise....

My glycol filled solar syatem should probably have this too, but it doesn't. I fill that from the top, then pressurise with a quick opening of a connection to the pressurised house system. Then that's valved off.

 

[trailhound68]

Put the backflow preventer in. One year later, drain some boiler water and look at it. Then tell me you don't need a BFP.
By the way, after three or so years, take it apart and clean the screen! You may think you have make up water, until your BFP is clogged. Damn..
Steam Ship Captain.

 

[BrownianHeatingTech]

If your backflow preventer is leaking, it's most likely just some contamination on the valve seat.

Shut off the isolation valves, remove it, and clean the sealing surfaces.

That's why it leaks - to let you know it needs service. But these are generally serviceable valves, and do not need to be replaced, if you service them when they first start to drip.

Joe

 

[slowzuki]

The backflow preventer is mostly there incase someone in the future treats your boiler with anti-corrosion products which are mostly highly toxic. The logic to me is, if I die, and my wife has the system serviced by any old person, what could be the result?

In my case I won't be providing a permanent connection to the boiler. That way if a service person comes and offers to do it for her he will have to install a BFP anyways.

Untreated boiler water gets gross and scummy with rust etc but it won't kill you. High iron in the water can give you the runs though so don't take a chug just for fun.

 

[pybyr]

FYI, thanks to the suggestions here, I did pick up a Caleffi fill valve/ regulator with an integrated backflow preventer.

you all helped me realize that it's a good safety feature, not just some form of complexity disproportionate to benefit or purpose

and that's the exact sort of quality feedback that I appreciate being able to get 'round here

thanks

 

[Tony H]

The backflow preventer is mostly there incase someone in the future treats your boiler with anti-corrosion products which are mostly highly toxic. The logic to me is, if I die, and my wife has the system serviced by any old person, what could be the result?

In my case I won't be providing a permanent connection to the boiler. That way if a service person comes and offers to do it for her he will have to install a BFP anyways.

Untreated boiler water gets gross and scummy with rust etc but it won't kill you. High iron in the water can give you the runs though so don't take a chug just for fun.

What about a chug for $15.00 we could take up a collection.

 

[peakbagger]

A home well system needs is as much or more than a minicipal. I have had pump problems twice where the pump wasnt pumping and the boiler back fed into the house system. Basically if the house pressure drops below boiler pressure and the there is a draw on the house, the pressure in the boiler can sometimes make it past a standard check valve.

Note a backflow preventer will leak on occasion, it is a sign that the valve is working correctly.