Black pipe to PVC connection

[tclat]

Hi,

On a design-build project, the DB has proposed using schedule 40 pvc pipe for the plumbing works. The MEP review consultant recommended schedule 80 pipe. As a compromise, the DB has offered to use schedule 40 black pipe (ductile iron?) with schedule 80 PVC bends which the reviewer has said is ok. This just does not seem right.

Any comments?

 

[cradlecat]

I have never heard of anything done like what is being proposed. If the reviewer approves sched 80 PVC on the bends then they should be OK with sched. 80 PVC throughout the pipe run. The elbows will be where most of the turbulence and pressure will hit before making the 90 deg. bend so you would want the best materials on the bend. I suggest that the reviewer might have missed some wording and thought they were getting schedule 80 metal pipe on the bends.

 

[rconner]

While much ductile iron pipe is indeed coated/painted "black", I'm not sure I would not necessarily assume that the Contractor is offering up as a substitute good quality ductile iron pipe. For decades at least in the plumbing biz "black" (iron) piper had referred to something else e.g. see

http://www.ehow.com/list_7576087_black-iron-pipe-uses.html,

that incidentally often is not supplied e.g. with internal cement mortar lining like ductile iron pipe.
In any case, I agree with the young cat that supplying a stronger metal pipe but with weaker pvc at the fittings (if that is what they are talking about), is a quite unusual (and perhaps as he infers not normal/or best practice).

 

[cradlecat]

I agree with rconner's statements about the black ductile iron pipe. You'd probably want to double check the contractor's intent. Sched. 80 PVC is very strong for most plumbing needs and you don't have to worry about corrosion. I would double check with the reviewer to see if PVC is what they meant by sched 80 pipe. If the reviewer has the same doubts about black iron pipe as do most of us, the reviewer could be expressing those doubts. PVC is used extensively for plumbing purposes as long as it is kept out of direct sun. It's also usually less expensive than the proper ductile iron in both product and installation costs. If PVC is to be buried in the ground, be sure to get the right soil composition and compaction requirements from the PVC supplier.

 

[bimr]

Suggest you find a DB and a MEP review consultant with plumbing experience. What is suggested is nonsense and will not pass a building code inspection.

 

[tclat]

Thanks for the comments.

Thought this didn't make sense. Is would seem to me that sch 80 pvc pipe would be much cheaper to install than this "black pipe" so the material cost of the iron pipe must be significantly lower for the DB to be recommending its use.

 

[cradlecat]

Or the DB already has it on hand and wouldn't have to outlay the cost to purchase.