Tie in installation into existing 8" main 4

[dbelov72]

Hello everyone,

There is an 8" pipe through which domestic cold water goes to the entire facility, which is an airport.
We need to tie in a massive washroom to it; however, we can't really shut down water for too many hours...

One of the alternatives is to tie in to another washroom, but that adds to costs way too much in the form of piping.

What could be the other options for that to consider?
The contractor claims that freezing is technically possible on an 8" pipe; however, it seems to cost a fortune...


Regards,
Denis

 

[pennpiper]

dbelov72,
"The contractor claims that freezing is technically possible on an 8" pipe"
What exactly does the "Contractor" mean by this. In my opinion (based on some experience) freezing the main line would be the same as shutting it down.

I suggest you consult with one or more experienced and qualified "Hot-Tap" Tie-in specialist contractors to see if there are alternatives to solving your problem.

Specifically ask them about "Stoppling" method of adding a Branch with out shutting down the main line. It is a valid potential solution.



Sometimes its possible to do all the right things and still get bad results

 

[Gator]

I presume someone has already done the hydraulics to ensure you don't starve the current water users.

There's no reason a hot tap cannot be done without a shutdown, especially for water service.

Stoppling is more for cutting out and removing a section of pipe while the line remains in service.

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[bimr]

A standard water main hot top is simple enough. Surprised that your Contractor does not know how to do this.

https://www.youtube.com/watch?v=v3MjC-thuik

http://www.municipalpipeservices.com/water-main-tap.html

http://pipingdesign.com/download/hot-tapping_stoppling.pdf

 

[dbelov72]

thank you for the informative replies!
just wanted to give you some details on what happens.

so, the hot tap would apparently be the most reasonable solution ever.
however, the it is the main pipe, made of ductile iron pipe.
by drilling the pipe, which is what hot tapping does, would bring a contaminant into the potable water flowing through the pipe.
this is the explanation from the contractor.
my mistake here was that I didn't mention the type of pipe and the fact that it is potable water that flows through it.

Also, for the freezing part: shutting down the water would not be possible for extended period of time (the facility I am working on right now is an airport). it technically could be done at night for couple of hours; however, draining would take a while...therefore, freezing two points and working in between would also be an option. the contractor said this option would not impress us in terms of pricing (I am still intending to get the pricing for this).

The option that everything is boiling down to is to bring the water into the washroom by tieing in to a branch pipes from another washroom. supposedly, the supply of water is enough. however, this option requires a hell lot of piping (almost 20 meters...) which motivates me to look hard for other options.

Thanks a lot!
One of the many big reasons I like engineering is engineers, people who know what they talk about. working hard on becoming one!

 

[dicksewerrat]

First of all, what size water supply do you need? Second, small service taps are made 100's of times every day. Third, there is no contamination of the original supply because the tapping machine is pressurized by the supply line and is opened to install the tap and corporation cock.
fourth,If you contractor doesn't know how to do this, hire a different one. 20 meters of pipe is not a lot, 2000 meters is a lot.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[Gator]

I think the "contamination" refers to cuttings/shards (not the coupon itself, of course) potentially falling into the run pipe and continuing in the flow to downstream users.

Piping Design Central

 

[bimr]

dicksewerrat is correct.

The hot tap procedure includes disinfection and flushing of the water main, Any certified water operator should know the procedures required.

Refer to the attached typical procedure. Note the reference to the AWWA standard. You might consider emplying a more qualifed contractor if this is a critical issue.

http://dnr.mo.gov/pubs/pub2442.pdf

Hot taps are frequently done by third parties. Hot taps are common procedures and done every day by potable water system operators.

 

[jgailla]

These are usually called wet taps instead of hot taps when used for potable water or sanitary force mains.
This is a very common procedure and I would be leery of any contractor who was not aware of it.
I still have the coupon from the first wet tap I observed.
Plus everything bimr and dicksewerrat said.

 

[dbelov72]

Just a little update on the topic.

So I ran the meeting today with everyone, us, the general contractor, owner representative, consultant, mechanical contractor.
Presented the following solutions:
1. Replace the section of the pipe
2. Hot tap
3. Freeze the thing and perform works
4. Tie in from a different (remote) location

The discussion fairly quickly boiled down to hot tap.
Client's concern was that the ductile pipe is not repairable; therefore, it is a contaminant. He then was explained that it is a super tiny contaminant that should not cause any stress.
His other concern was that they had a hot tap on a PVC pipe; the coupon got sucked in by water into the pipe. Although it didn't cause any negative consequences, the owner still thinks bad of hot taps.

The whole story was an interesting learning experience, especially for myself, who is a civil with an interest in mechanical.

Thank you everyone for your replies!

 

[jgailla]

That doesn't sound right. How can a pressurized pipe suck a coupon in?

 

[PEDARRIN2]

Is this on the water service (upstream of the backflow prevention) or on the domestic water piping.

I cannot speak about the water service - they do things differently than the domestic system.

if you to a wet tap, the procedure to disinfect and flush the system will require lots of water being wasted (the entire system), given that the system is not being taken out of service.

If this is on the downstream side of the backflow preventer, the applicable portion of piping needs to be taken out of service, drained, disinfected and flushed. this can be accomplished by also installing small drain cocks on the piping and using them as entry/exit points of the fixed system.

Talk to the plumbing inspector since he will be the one approving the work.

 

[dbelov72]

possibly it didn't attach itself to the drill properly

 

[bimr]

Actually, the 20 meters of pipe is probably less expense than the cost of the hot tap. 20 meters of pipe is just a little pipe, not "a hell lot of piping (almost 20 meters...)".

 

[bimr]

Here is an attachment that shows a hot tap of a 90-Inch water main, also at an airport. Note the picture showing the wires that hold the coupon on the drill bit.

 

[Gator]

I don't see any "wires that hold the coupon on the drill bit" in bimr's photos.


Piping Design Central

 

[bimr]

Try this:

 

[dbelov72]

bimr,

If it was, we would totally go for that option, I wouldn't search for other solutions, and we wouldn't have that meeting.

Although, it sounds simple and looks easy on the drawings, this is what happened:
The 20 meters of piping need through different rooms, that contain mechanical equipment (baggage conveyors). It is hard to go through those rooms, since it is very very tight; how they wanted to install pipes in there, I still don't quiet imagine.
Pipes go up and down, they need to be cut, since they are supplied originally way too long; thus, there is a whole bunch of elbows, reducers and other things. The submitted material thing itself included an entire A4 page of things that need to go in there; therefore, we only got material cost for $25000. Plus, there is a labour cost, which is 60 manhours in best scenario... Lockouts, scaffold, defects - all this stuff has indirect costs in it as well.
In contrast, hot tapping takes only to get the machine up to the pipe, get the saddle on, drill the thing, and get it working. $3000 tops.

 

[bimr]

Understood. Looks like your biggest problem is project management ie. herding all of the cats.

 

[Gator]

Ah, OK, the spikes.

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