Dry Pipe Valve - Main Drain for full flow?

[JCianfarra]

Hello Forum,

In a case where you have a 4" dry pipe valve on an upper level of a building and the 2" 'Main Drain' discharges into a 4" floor drain, does this floor drain need to take a full flow test or is the 2" drain simply for system drainage purposes. If I had a standard wet sectional valve, my drain assembly would have provisions for testing my alarm initiating device and also a full bore drain assembly for emptying the system. Is the drain on the dry pipe system valve considered a 'Main Drain' in terms of conducting a 'Main Drain' test for measuring pressure drop under flow conditions?

Thanks! JLC

 

[chicopee]

You'll see this situation in basement and in the case that you stated. In the past when I tested 2" drains , I never took into consideration what you are stating and some of the worse scenarios was to flood the basements and stop the tests. The only consideration is whether you have a short, intermediate or long drain pipe; if you feel that the back up should be considered, then assume a long 2" drain. If you feel that the 4" floor drain backup excessively then you can not conduct the test and you would make a recommendation to lengthen the drain pipe or have it safely discharge somewhere else. After all a 2" drain test is an estimation, and not an accurate measure, of the water availability to the sprinkler system.

 

[cdafd]

"""Is the drain on the dry pipe system valve considered a 'Main Drain' in terms of conducting a 'Main Drain' test for measuring pressure drop under flow conditions?""""

I would say yes required for the annual main drain test.

Yes should be piped to outside or legally piped to a drain that can handle the wide open valve

 

[JCianfarra]

The wording for the 'Main Drain Test Connection' says it "...shall be provided at locations that will permit flow test of water supplies and connections." So if this is the case if we are considering the piping from the fire pump up to the attic part of the 'Water Supply', it seems as though we need to do multiple 'Main Drain' tests. I this particular project that then would require a 'Main Drain Test' at the fire pump in the basement, the sectional dry pipe valve group in the basement, the dozen or more sectional valves off of the seven risers, and finally a 'Main Drain Test' performed at the dry pipe valve group on the top floor for the attic. Hmm...That would sure be a whole lot of 'Main Drain' tests to perform on one building.

 

[cdafd]

Ok now you are changing the op

Is this just a general question or actual system you are looking at?

Not near the book, but you need a drain for each system.
And would have to see how the main drain test requirement reads

 

[JCianfarra]

Cdafd, This is a question about a specific system, and ultimately about all systems in general. After I saw the answers I figured that my describing it as "...a 4" dry pipe valve on an upper level of a building" and asking if "...the drain on the dry pipe system valve considered a 'Main Drain'" was clear enough. The questions was not if a 'Main Drain' test had to have provisions to handle full flow. The question is if the drains on the section valve groups are considered 'Main Drains'. Our project manager has had Fire Officials ask him to conduct full flows for this type of location which brought up the subject, however that does not mean that it is a required test. A 4" floor drain is specified for this location on the 4th floor which would be fine to use merely as a drain. Thanks again - JLC

 

[cdafd]

Maybe if the valve is just cracked and not full open

Suggest direct connection designed to the plumbing code for direct connection

 

[JCianfarra]

I'm sorry but I don't understand the comment "Maybe if the valve is just cracked and not full open". If its just used as a drain connection there is not issue, however if it is used as a 'Main Drain' test there is ~140 psi behind a 2" valve so it will still be one heck of a crack. And you can't just crack a valve to perform a 'Main Drain' test because you need to flow enough water to show any comparable loss in pressure which is the purpose of the test. And a sprinkler drain is not allowed to be connected directly to a waste line; especially one that would be under pressure. There must be an air gap so the waste line in not pressurized and there would probably also be issues with cross contamination.