Sanitary Wye

[trashcanman]

Where can I find data on pressure drop through a sanitary wye? Equivalent length or K-factor will do. Thanks. (I have already searched the forum - no luck).

 

[PEDARRIN2]

Typically a sanitary wye is not used on a pressure system - so there would not be a listed pressure drop.

Depending on the flow direction, I would probably estimate it as a either a tee flow through a branch or a bull head tee.

 

[SNORGY]

There is anentire section devoted to flow through tees and wyes in Crane TP-410, (C)2011, Chapter 2, Pages 2-14 thru 2-16.

 

[trashcanman]

I meant exactly as posted. Sanitary wyes are under pressure in siphonic roof drainage systems.
I already have lots of data on regular tee fittings.
Any Euros with that data? Thanks.

 

[katmar]

How tight is your design? The envelope that you are looking in is probably bounded by a standard bull nose tee on the high side and a 45 degree mitre bend on the low side. Depending on the size and flow rate you will find K-values in the range of 0.7 to 1.1 for the tee, and about 0.3 for the 45 degree mitre bend. So I would guess that a number of 0.5 to 0.6 is reasonable for a wye. Idelchick is one of the few sources of K-values for wyes. His numbers are similar, assuming you are working with equally sized legs and the branch is at 135 degrees.

If your velocity in the pipe is 1 m/s then the velocity head is 51 mm of water column. An absolute error of 0.1 in the K-value will therfore change the pressure drop by 5 mm WC. If your design is this tight then you need to determine the pressure drop experimentally for your specific geometry. If you are working with pressure drops in the range of several inches or centimetres of WC then the error is likely to be negligible.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[PEDARRIN2]

Most of the siphonic roof drain manufactureres have software that enable you to design/size the system.

Also, ASPE Tech Standard 45 "Siphonic Roff Drainage" should offer design assistance/guidance.

Some of the designs I have seen did not use sanitary wyes since siphonic drainage is a "pressure" system so using drainage fittings which assist in flow of gravity systems may not be required. Most jurisdictions require siphonic drainage to be an "engineered system" so use of drainage type fittings may not be required.

I agree with katmar that the K value will be somewhere between a bull nose tee and a 45 or 60 degree miter bend.

 

[katmar]

If you are using the wye in combining mode rather than diverging mode then please disregard everything I wrote earlier. Depending on the relative flows in the combining legs the k-value can vary from negative (effectively a venturi vacuum pump) all the way up to > 5.0. Get specialist advice.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"