# 4" Force main leaking?



## guyute65045 (Nov 23, 2006)

Testing my 4" force main 270' and cannot get it to hold. I get it to 77psi and it drops back down to 65, over and over. Keep getting air out of the line as well. I worked at it for 5 hours yesterday and it kept spitting air, left it charged overnight and it held 60psi. I would think if it was a leak it would go to 0 no? I really am not looking forward to digging up all the joints, but I will start with the one that was a bear on Monday. Anybody have any similar experience with this, I have to think maybe there is a small dip in the line giving me my problems.:confused1:
Thanks,
John


----------



## dayexco (Mar 4, 2006)

slow leaks are a s.o.b.....and the pits of it is, if it's in an open area, at 270'....you really can't afford to...at least with our margins here...hire somebody to come in and find it for you. first thing i'd do, is dig up any mechanical joints, or glue joints you made...they typically will fail easier than a push on gasketed joint. other than that, if you're using 20 or 40 footers, you got some joints to dig up. you "might" want to if you're joint hopping, dig at the mid point, cap off both ways, throw 10 psi air to it, see if it holds, that'll narrow it down which way it is...sorry to hear about this, i've had a few thru the years...they are time consuming, costly, and pure and simple...peeese you off. good luck


----------



## guyute65045 (Nov 23, 2006)

There was the "one" joint that was a PITA. isnt there always one.


----------



## Dozerman56 (Dec 11, 2009)

If you didn't bed it in stone it may bubble to the surface if you keep the pressure on.


----------



## S.R.E. (Apr 8, 2010)

Well, I would stop and think first.
1. How are you filling this line (Do you have a double check valve on the source?)
2. How are you restraining the ends and fittings?
3. If you had one bad joint I would definitely check there. A rolled gasket will eventually go together if you fight it hard enough, but it will leak there.
I could go on with lots more questions, but maybe you could describe what kind of pipe you are using. The type of joints on the pipe, fittings, and how you are filling and testing this pipe.


----------



## WC&T (Feb 22, 2010)

Whats the working pressure of the existing line you are connected to? If you are testing against a valve it might be leaking by the valve until you hit the working pressure of the existing line. Could be as simple as a rock or something small stuck in the valve. Then again if it damaged the valve than it isn't so simple.


----------



## guyute65045 (Nov 23, 2006)

1. 4" SDR 21 with gasketed joints
2. The pipe is run from a valve pit up next to the old pump station that will be abandoned in place
3. It is one long run of 250' up a hill, bends 45* and goes under the road, bends one more time @ 15' 45* then there is a short piece that 90's up to where we are testing.
4. Test is being done from the top as that is the only way to fill it, bushed the pipe down to 3/4 and then hooked the hand pump tester to it, we are using house pressure to get to 65, then hand pumping the rest of the way.
5. All joints are gasketed except the 90 is glued. the 2nd 45 was a bear to get on(going under primary power and cable, and over fiber). I plan on swapping the 45 out on monday and checking the 90 when I do. The pipe is all bed in 3/4" stone.


----------



## S.R.E. (Apr 8, 2010)

Air in line: When filling line you need to let the air out as you fill. If filling with a garden hose I would fill from the highest elevation by just sticking the hose into the 4" pipe and let it run until the water flows out. As it fills the air should be pushed out around the gaps between the garden hose and the pipe. Let it sit for about an hour to see if any air works its way out. Top off water. Now bush down to 3/4" and hook up you tester and pump away. Can you shut of the line between your pump and the line you are testing? I always put a special testing setup that I built so I can shut off supply line with a ball valve and between the ball valve and the line I am testing I have a tee for my gauge that I can shut off(so when you pin it you can change it out without lowering your pressure or dismantling your setup). I also have a tee in between there that has a ball valve on it for bleeding air out of the system.
What pressure are you trying to test at? How is the pipe restrained?? Thrust Blocks behind 45s? You might check the pipe where it enters the old valve pit and see if maybe it has popped out of the bell there. Also what are you testing against at the end in the valve pit (old valve?, blind flange?, cap? or what?). 
I remember one time we were testing a waterline and we couldn't get it more then 10 psi above static pressure. We checked every joint and found that the last one had pulled out enough for the water to get by the gasket. The temporary blocking we put in to hold the thrust just wasn't strong enough. Now I always put reverse concrete thrust blocks at both ends (Unless using other restraints) even if they are only temporary.


----------



## PipeGuy (Oct 8, 2004)

guyute65045 said:


> ...I get it to 77psi and it drops back down to 65, over and over. Keep getting air out of the line as well.I have to think maybe there is a small dip in the line giving me my problems.:confused1:
> Thanks,
> John


If you're saying that 77psi is a threshold at which point the pressure consistently drops off some fixed amount before beginning to re-pressurize then that's typically indicative of a crack in something that won't open up with less than a certain pressure on it. Ductile iron pipe with casting defects will demonstrate that kind of failure albeit usually at a pressure in excess of 100 PSI.
Given your description of how the line runs (one long run of 250' up a hill) I don't see how air could be a problem unless it's trapped right against the fill point. A tee and a valve at the fill point is an easy enough way to vent air without continually disconnecting the fill supply / test pump.
There's no easy way to find leaks. Sometimes cutting and capping a line into increasingly smaller segments is a practical way to begin isolating the point of failure - sometimes it's not:sad:.


----------



## S.R.E. (Apr 8, 2010)

Did you find your leak? Let us know how it turned out.


----------



## guyute65045 (Nov 23, 2006)

I am still fighting with this thing, I put dye in the line and found a steady drip in the valve pit, 1 drip every 30 sec. I took the himax outside the valve pit apart and drained the line, capped filled with 15psi of air. No leaks, no loss of air pressure. I am baffled, I switched all fittings out, checked for leaks at each fitting with air and water pressure nothing. I left last night with the line pressurized to 95psi, and checked this morning and it was down to 75, and there was a good puddle in the valve pit. I have the precast co coming to swap the sch 80 fitting that is leaking Monday. I hope that is it. I am ready to drop some dynamite in the pipe and walk away.
I need to get this thing passed and move on, that project is cursed  every contractor on the job has had some sort of problems.


----------



## S.R.E. (Apr 8, 2010)

Thanks for responding. Sorry to hear that its not fixed yet. If the problem is from the precast company you might be able to back-charge them for your time.(Good luck on that):whistling


----------



## PipeGuy (Oct 8, 2004)

guyute65045 said:


> ....1 drip every 30 sec. I took the himax outside the valve pit apart and drained the line, capped filled with 15psi of air. No leaks, no loss of air pressure.


What's your test gear set up? Is the line completely disconnected from everything or is there a possibility of loss through an isolation valve or through your test equipment?
15PSI isn't going to force open a defect that otherwise doesn't appear until 77PSI.


----------



## guyute65045 (Nov 23, 2006)

PipeGuy said:


> What's your test gear set up? Is the line completely disconnected from everything or is there a possibility of loss through an isolation valve or through your test equipment?
> 15PSI isn't going to force open a defect that otherwise doesn't appear until 77PSI.


I wanted to charge it up a bit more with the air but the tester(have to have the test done by a testing agency per spec book) was adamant about it being dangerous using any more then 10psi of air. I pumped it up to 15 not wanting to cause a boom.

The pipe run is as follows:
The pipe comes out of the valve pit(valves are all cranked down) theres a hi-max right there then 8-10 sections(20ftrs) running straight up the hill. it bends 45*(now an MJ fitting) runs about 20-30ft to another 45* MJ fitting then to a glue on 90* about 6 ft away and the end terminates above ground where we are testing. All fittings are braced, and have been checked under pressure, I did have one 45* that was cracked the other was solid but I swapped out anyhow.
The testing set up: 
4" coupler, bushed down to 3/4" with all glued fittings. 3/4" pipe,T, Valve-guage assembly with bleed off nipple, other side of the T there is another valve and a fitting to attach the hose or pump. I have checked the test set up for leaks, and found none. the T and all other parts are Iron fittings. I am going to try a 3rd gauge on monday.
We are using the house pressure to get it up to 65psi then the pump to get to 77. On the recommendation of an engineer friend I pumped it to 100 on friday afternoon, this morning it was at 75 and there was a good amount of green water in the bottom of the valve pit.

The weird thing is that on Wed it held 75# from 8am to 12:30 while I was filling the 3500gal force main tank for a leak test. As soon as the water level reached the level of the valve pit the pressure on the line started to drop. I had the valve pit isolated from the tank with a test ball except for the piping inside the pump station that connects to the valve pit. Probably a coincedence but who knows, I am totally baffled. It would be really easy for me if it was in fact the schedule 80 fitting in the valve pit, but I don't know if that drip/frequency is enough to cause that much pressure loss.


----------



## PipeGuy (Oct 8, 2004)

It doesn't take much water loss to cause a substantial reduction in pressure once the test section is completely purged of air. That being said, I wish I had a nickel for everytime I discovered that leaky seals in a piston pressure pump or a bad check/ball valve was the source of an otherwise unidentifiable leak.
My experience is that accomplishing an uneventful acceptance test on a small diameter PVC pressure sewer is like finding a pearl in an oyster - its a joy when you get one but you should hardly be surprised when you don't.


----------



## S.R.E. (Apr 8, 2010)

guyute65045 said:


> The weird thing is that on Wed it held 75# from 8am to 12:30 while I was filling the 3500gal force main tank for a leak test. As soon as the water level reached the level of the valve pit the pressure on the line started to drop. I had the valve pit isolated from the tank with a test ball except for the piping inside the pump station that connects to the valve pit. Probably a coincedence but who knows, I am totally baffled. It would be really easy for me if it was in fact the schedule 80 fitting in the valve pit, but I don't know if that drip/frequency is enough to cause that much pressure loss.


I know that there is a formula that could tell you how much water loss would cause that loss of pressure, but I don't know what it is. Sometimes a fitting or valve or cracked pipe will not leak until over a certain P.S.I so It's possible that it is in the pit. Could you disconnect the valve and cap it for the test? Most Authorities around here won't let you test against a in line valve.


----------



## guyute65045 (Nov 23, 2006)

Well I am off to test this thing again. I did two trial runs yesterday with 0 pressure loss over 2 separate 2 hour periods. Now lets see if the %$#^ pipe will do it while the engineer is there.


----------



## waldrop (Jan 3, 2010)

did you get your test off? if not pump that b----- up to 250 she either blow or go


----------



## Kgmz (Feb 9, 2007)

Pipeguy is right, it doesn't take much water loss.

We once had a pesky leak like that in a water main. Dug around for 2 days and couldn't find it and was about to call the leak detector guys. But then I decided to check the piping going to the blow off at on end of the main branches, dug down to follow the 2" pipe going down to the main and found a treaded joint with just a few drips coming out. Took it apart to check threads, put it back together tighter and no leaks after. So yes a few drips will cause a substantial loss of pressure.


----------



## guyute65045 (Nov 23, 2006)

passed yesterday, 0 pressure loss. Must have been a valve not seating properly. Doing my tie in tomorrow and getting off that job :clap:


----------



## S.R.E. (Apr 8, 2010)

:thumbsup: Good thing you had a week in your bid for testing.:whistling Well on to the next one. I always tell my guys that if a pipe joint doesn't look or feel right going together it's easier and cheaper to take it apart right there and check it. Thanks for the update.


----------

