Need some Wethead help Please

Alan R. Mercurio

Hello friends, I'm currently in NY working with some of my fellow technicians in the field passing along some the procedures that have proven to be successful for me during my time in this trade.

Any how we seen something today and the guys and I were wondering what the purpose of this was? I told them I didn't know. but that they should never be embarrassed to ask questions when they are unsure.

I told them I would bring our question to you folks and I'm confident the knowledge would be shared.

So here goes. We seen a backflow preventer today installed just before the water feed valve (prv) only this one was different then any other I have seen before. this one had a vent on it? This was a 1/2" Backflow Preventer with and intermediate atmos vent. Model 9D-M3

Our question is. what is the reason for the vent??

Thanks friends I look forward to the education.



Your friend in the industry,<BR>Alan R. Mercurio<BR><BR><a href="http://oiltechtalk.com">Oil Tech Talk</a>

Unknown

We used those in NH

If a water main broke in the street, the vent would relieve the vacuum and the boiler water would stay in the boiler.

Anytime the outlet pressure exceeded the inlet pressure, they'd drip on the floor, by design.

It's two check valves with a vent in between that is also a check valve, sort of. Hard to describe.

It lets the boiler fill, it vents the supply if the boiler pressure exceeds the street pressure, and the street draws a vacuum, and it eventually fails and needs service.

Noel

Pat Clark

We use them here in Anchorage

Required by code, Noel is right about the vent.

Pat

ScottMP

Watts 9DM3

Alan we have to install those by Mass code. I am suprised you hav'nt seem one before. We usally use a combo unit the 911S which is an auto-matic feed and backflow preventer. They are designed for low flow situations

Noels right they leak on the floor when there is a backflow situation ( also sometime not ).

Unless the fill valve is closed these should be installed on every boiler for protection of the water supply.

Scott

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Alan R. Mercurio

Thanks Guy's

I appreciate the education and the prompt response. You folks are the best!

Your friend in the industry,
Alan R. Mercurio

Oil Tech Talk

Unknown

Scott , is the backflow

with the vent required by code ? I remember using them in the city and they vented on the floor ALOT . Steam and hot water boilers . On the Island we switched to the backflow without the vent and it passes code here .

Floyd_5

try this.

see if this works...
Here's all the poop on that puppy!

ScottMP

Good Question Ron

I am not sure but will find out. You get so use to using a product, it becomes second nature.

I seem to remember a problem with leaking in the begining. Some guys would fix it by putting a plug in the vent, nice huh ?

This is one of those things that happens so rarly but the consequence could be huge. Theres a fire down the street and creates a backflow, while mom fills the bottle for her baby with boiler water.

Interesting bit of Mass Plumbing Code "2.14 (g) Water connections to Heating Boilers. Potable water connections to a heating boiler shall be provided with an approved back flow preventer or air gap in the water line to prevent a cross connection. Backflow preventers shall not be required on manually controlled water lines to residential type steam and/or gavity fed hot water space heating systems."

Not required on manually controlled lines to gravity feed but no mention of a forced hot water system with a closed ball valve. More than likly to stop some one from leaving the valve open, but why is it O.K. on a gravity system ? Maybe they think the pump will push it into the potable water supply, but the backflow could still occur.

Scott


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Uni R

Scott...

"Interesting bit of Mass Plumbing Code "2.14 (g) Water connections to Heating Boilers. Potable water connections to a heating boiler shall be provided with an approved back flow preventer or air gap in the water line to prevent a cross connection. Backflow preventers shall not be required on manually controlled water lines to residential type steam and/or gavity fed hot water space heating systems."

Not required on manually controlled lines to gravity feed but no mention of a forced hot water system with a closed ball valve."

I'm thinking by "gravity fed" they don't mean the actual heating circulation, they are talking about open an fill/expansion tank in the attic.

ScottMP

Thats

Probable it. Makes perfect sense allthought some of the guys here have never seen the open tank in the attic .

Scott

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