Flex Drop / Flex Head as Return Bend?

[RemoteControlFF]

Has anyone thought about using Flex Heads as return bends in a heated area attached to a dry system?

I can't find anywhere in NFPA 13 that states exactly what the arrangement of a return bend must be and in my mind if the tubing had a similar rise, run, drop return bend it would be meeting the same role as a standard return bend. The obvious labor advantage is huge, so I can't imagine I'm the first one to think of it.

Anyone have any ideas/guidance/experience doing this?

 

[cdafd]

just says connected to the top

only other thing I see is the flex could bend a little more and maybe not give the angles rigid pipe would, so would possibly defeat the purpose of a return bend???


cost would seem to be the driving factor.

oh but wait forgot to ask webster:

A pipe fitting, 1 or a preformed piece of tubing which provides a 180° change in direction.

and
design engineering) A pipe fitting, equal to two ells, used to connect parallel pipes so that fluid flowing into one will return in the opposite direction through the other.

 

[RemoteControlFF]

I called Viking tech support and they said it was no problem to use it in that way, however only the flexhead installation guide mentions that they are "intended for use in hydraulically designed wet, pre-action, deluge or dry pipe sprinkler per NFPA 13, 13R, and 13D
guidelines."

This still punts the question to the designer/AHJ -- I'm mostly worried that a compliance inspector comes through and decides that the bends aren't square enough (an arc instead of 2 90s with a flat bit) or something like that and I have to send fitters back to square off the drops into a "return bend like" arrangement.

cdafd: As for cost being the factor, I agree - if I have the chance I'm using flex heads for sure. It will mean I double my material cost, per drop but I'm saving a ton of time, and pressure testing before everything gets locked up behind hard lids is great.

 

[stookeyfpe]

Nope. I wouldn't allow it. It was never the original intent of the original design - and - with 3 different manufacturers and the original manufacturer suing the other two (hint: Viking was not the original manufacturer or holder of the patent), you are entering into an arena where the flexible hose as a return bend violates its original listing.

I would not touch anything but the original Flex Head with the other two manufacturers being sued as a basis for design.

The listing reports don't say return bend anywhere - or am I wrong on this also?

 

[coarts]

The only reason for the return bend would be to keep sediment out of drop, so if its attached to the top of tee or 90, its still going to have the same result as hard piping and should be in compliance [for my 2 cents].

 

[SprinklerDesigner2]

I agree with Stookey.

I looked into it once but everything I ran across referred to wet systems.

 

[RemoteControlFF]

stookeyfpe: The lawsuits aren't my concern. If a court finds that Viking (or any other company) violated the intellectual property rights of Flex Head, that will not cause some repo man to come onto the job and rip out all the "knockoff" products. There is a bit of an ethical question here, not quite as clear as buying a bootleg DVD, but we can always take up that discussion in the "Professional Ethics in engineering" forum.

That said, the fact that there is no mention of return bends in any manufacturer literature, and only one sheet mentions "dry systems" in passing is a bit concerning to me - but it is possible that they consider it a "no brainier" that this component could be used as a return bend and don't bother to spell it out. I am a bit skeptical of that idea, however.

 

[stookeyfpe]

I'm a purist when it comes to listings. I think it is a violation of the listing and therefore a violation of NFPA 13 and the IFC. If you believe otherwise, proceed as you see fit.

In my world I only have about 5-10 years of experience with these flexible hoses. Yet I have at least 100 years of carbon steel pipe. Being the conservative, albeit anal person I am, I'll stick with Schedule 40 pipe for the return bends and then connect the flexible hose if that is what the design calls for.

Please don't take my response as sarcastic - I'm just offering answers to the questions being posted.

 

[RemoteControlFF]

I'm sorry if I came off as dismissive - I'm trying to get to a solution that is best for my budget and treats the client right. I understand your concerns with the flex hose connections, For the same reason I dislike using ultra-thinwall pipe, I just don't think it will last the way a sprinkler system should.

Flexhead stated that the their system is OK for a dry system (Page 5 of their submittal package) and the other vendors I have spoken to said the same thing.

I'm planning on using them, I now feel comfortable with the decision - thanks for everyone's input.