Minimum Pipe Length Between 45 Bends

[aliciam]

When making a 90 degree turn in pipe and using two 45s, is there a standard minimum pipe length for PVC (mechanical joint ductile iron fittings)? Does the length vary depending on the diameter of the PVC?

 

[aliciam]

That is minimum pipe length between the fittings. Thanks.

 

[jgailla]

For potable water or sewer force main PVC, you should just need room for joint restraints.
Three feet should be fine for the minimum distance between fittings on pipes up to 12" diameter. I think you need to go to four feet for 14"-16".
You can find dimnesional information on restraints at ebaa.com.

 

[bimr]

There is no minimum length between fittings. You just will need to have adequate room to tighten the bolts.

You can probably get by with as low as 6-inches, but it will depend somewhat on the specific mechanical joint restraint that you will employ.

http://www.ebaa.com/PDF/Brochure.2000PV.pdf

 

[rconner]

If you don't see this issue covered in EBAA Iron's literature it may not be a bad idea to give them a call and ask them this question directly. If the bends are in the same plane, a very short spool will result in wedges exerting in effect double radial forces essentially at basically the same "clock" location/line on the very short pipe spool. I believe PVC, even of the heaviest schedules, has limited ability to in long-term handle localized loads at notches etc. (and maybe glands shouldn't be messed with at all under pressure, as taught e.g. graphically in at least extreme case at

http://www.oshrc.gov/decisions/alj_pending/08-1225.pdf

).

All that being said, I guess there could be some lesser concern with say DR13.5 or 14 4" pipe at very low pressure than with much larger diameter pvc pipe at very high and cyclic pressures? [Remember also if you put the two 45's very close together, you essentially have a 90 degree pipeline bend, and the "45" length of restraint in either direction off that compound bend may not be adequate or safe).

 

[aliciam]

Thanks for your replies. As a general rule of thumb we try to keep spool pieces at least 2 feet long. I overheard someone today say no spool pieces less than 18" long. I may just call and see if they have specific guidelines.

rconner - Ouch to breaking both legs!

 

[bimr]

It will depend somewhat on the particular manufacturers joint that you are using, but the megalug joint for example does not transmit radial forces onto the pipe. EBBA Iron states that the thrust load is primarily longitudinal.

Here is a brochure describing the history of the megalug for ductile iron pipe:

http://www.ebaa.com/PDF/Connections.DI-02.pdf

The wedges on the megalug are typically 4 to 5-inches apart which gives an indication of the zone of influence of the restraint on the pipe.

I agree with rconner that it is best to call the manufacturer of the restraint that you plan to use and get technical advice.

 

[SteveWag]

You may want to keep in mind the “Foster” fitting or adapter. We have used them for years. They allow coupling two MJ ends without a spool and are inherently restrained. No glands at all and only one bolt kit. Very compact.

http://www.ejprescott.com/media/reference/FosterAdaptorB-10.pdf

Steve