Weird Waste Pipe Woes

[doorframe]

As Mike S has got his waste pipe issues sorted, I've got a waste pipe issue that's a bit on the weird side.

The 4" plastic soil stack goes from the garage floor through 2 bathrooms above, then through the roof to the vent (it's a town house with 5 split levels). Everything runs away perfectly (bath, shower, sinks, w/m, d/w, kitchen sink etc).

But, when the d/w is running, at certain points during the operation the soil stack goes 'BANG!', as if it is being hit with a mallet. You can even feel the thud if you have your hand on the pipe (in either of the bathroom cupboards where it is accessible). The d/w waste goes to the kitchen sink waste 'U' bend, in conventional fashion, and from there a flexible pipe takes it through the wall into the garage, where it joins the stack. I originally thought the bang was from the cold pipe as the solenoid valve opened and closed, but it's definitely from the plastic stack.

Any ideas? We run the d/w at night when we go to bed, and it's the only thing running in the house, and the banging is driving me mad.

 

[Monkey Mark]

It could well be a partial blockage. I've seen similar a few times often caused by plastic bags, wrappers etc. It blocks the flow, at least to some point, and fills with water. When it's full it can block it completely then the pressure forces the bag our of the way. This can cause a noise as it empties and the process repeats.

Funniest one was at a really prim ladies house. She scurried off when the offending article was found to be a condom.

 

[doorframe]

Mark, do you mean a blockage within the d/w?

There no bang from the d/w at all. You can stand beside it in the kitchen and hear nothing. It's definitely something to do with the drain cycle though.

The old d/w (can't remember the make) was on the same pipe system. Only since we got the Bosch have we had the issue. My 'best' solution (possibly dumb idea) is to re route the waste direct through the wall (not via the sink waste) and into an open topped 'U' bend, the same as the w/m. The pipes are very conveniently positioned for this.

 

[Zeddedhed]

Sounds to me like it will either be due to thermal expansion of some sort or suction/vacuum problems.

I don't know much more than that but most of the pipe noises I've come across in my time have been related to one or the other.

 

[Monkey Mark]

Mark, do you mean a blockage within the d/w?

There no bang from the d/w at all. You can stand beside it in the kitchen and hear nothing. It's definitely something to do with the drain cycle though.

The old d/w (can't remember the make) was on the same pipe system. Only since we got the Bosch have we had the issue. My 'best' solution (possibly dumb idea) is to re route the waste direct through the wall (not via the sink waste) and into an open topped 'U' bend, the same as the w/m. The pipes are very conveniently positioned for this.

No, I meant more likely in the waste pipe but before it joins to kitchen sink waste.
If its only been happening since you changed to a new DW, perhaps during the swap something, maybe part of the plastic wrapping, managed to get into the pipe?
You could always set up a temporary waste via something like a hose pipe just to see what happens. If it's still making some sort of noise then you can rule out the waste pipe.

 

[Phil Pascoe]

"Mark, do you mean a blockage within the d/w? "
I've just had a vision of someone putting their condoms through the dishwasher. :lol:

 

[Monkey Mark]

"Mark, do you mean a blockage within the d/w? "
I've just had a vision of someone putting their condoms through the dishwasher. :lol:

Wash and re-use. Surely im not the only one that does this? :lol:

 

[Distinterior]

Doorframe,

You say the D/W is a Bosch? and this noise didn't occur with the previous D/W fitted?

Does it have one of these fitted on the water inlet pipe connection?

http://www.spares4appliances.co.uk/dish ... AnFx8P8HAQ

If so, these are an Aquastop device that electronically opens and closes the water supply to the D/W by means of a solenoid when told to do so by the D/W itself. If your existing Cold water pipe is running in very close proximity to your 4" soil pipe, then when the valve opens or closes it could vibrate/clunk enough to hit the 4" pipe and make it seem as though its the 4" pipe that's thumping but the reality may well be that its the Cold pipe that's causing the problem.

Just a thought!!!

Tim.

 

[MARK.B.]

"Mark, do you mean a blockage within the d/w? "
I've just had a vision of someone putting their condoms through the dishwasher. :lol:

Wash and re-use. Surely im not the only one that does this? :lol:

Yeah but do you hang em on the line to dry :-# :lol:

 

[Phil Pascoe]

It reminds me of the old episode of Coronation Street where the woman picks up something off the dining room table - what's this? she says. It's a rectal thermometer, says Blanche, at which point the other woman drops it. Oh, don't worry, Blanche says, it's been through the dishwasher. Coronation St. humour at its best.

 

[Deejay]

Doorframe,

You say the D/W is a Bosch? and this noise didn't occur with the previous D/W fitted?

Does it have one of these fitted on the water inlet pipe connection?

http://www.spares4appliances.co.uk/dish ... AnFx8P8HAQ

If so, these are an Aquastop device that electronically opens and closes the water supply to the D/W by means of a solenoid when told to do so by the D/W itself. If your existing Cold water pipe is running in very close proximity to your 4" soil pipe, then when the valve opens or closes it could vibrate/clunk enough to hit the 4" pipe and make it seem as though its the 4" pipe that's thumping but the reality may well be that its the Cold pipe that's causing the problem.


Just a thought!!!

Tim.

Morning all

I have a Bosch dishwasher with a solenoid fitted, as Tim suggested.

The plumbing in my house was done 'frugally' with minimal support for the piping. When I first fitted the d/w, I connected the water supply to the indirect hot water, which was under low pressure.

When I had a combi boiler fitted, I replumbed the supply to the cold, at mains pressure.

Result - terrible water hammer when the solenoid closed.

Solution - restrict the flow using the service valve.

Worth a try.

Cheers

Dave

 

[doorframe]

There's no flow or pressure reducer fitted. I ruled this out as it bangs at the plastic waste soil stack, not the cold pipe, and the noise is not (it appears) when the machine fills, but when it is doing other things. But I'll try anything. I can easily turn the 1/4 turn isolator down to reduce the flow and try that. Our pressure is over 4Bar, so quite high. I'll adjust it when I get home from work later and see how it goes.

The soil stack is firmly fitted along it's entire length. The waste from the sink/dishwasher goes into it about 6 inches above the concrete floor, where it then joins the ceramic piping to the main drain.

The soil pipe doesn't come into contact with the cold feed anywhere.

Does anyone know roughly how much water a dish washer uses during a typical wash? I was thinking I could hang the drain pipe over a large bucket, so not connected to the waste in any way, and see what happens.

Thanks for all the suggestions.

 

[woodpig]

Just a thought but the two worst times to run a DW or WM is at night or while you're out. I laugh at folks who tell me they do this but it's their choice I guess:

http://www.theguardian.com/money/2014/j ... appliances

 

[n0legs]

Does the soil pipe have an open vent or an air admittance valve?

 

[Phil Pascoe]

Just a thought but the two worst times to run a DW or WM is at night or while you're out. I laugh at folks who tell me they do this but it's their choice I guess:

http://www.theguardian.com/money/2014/j ... appliances

There must be millions (like me) on economy 7 that only run them at night ...

 

[Deejay]

Afternoon Doorframe

Does anyone know roughly how much water a dish washer uses during a typical wash?

Mine uses about 11 litres, depending on the wash cycle. The Bosch site will give you the figures for your machine.

Try it on a rinse cycle (which is cold only on my machine). I wonder if it's something to do with heat expanding the soil stack pipe(s). There should be some slack left at the joints to allow the pipe to move within the sockets, but if the slack isn't there, the pipe might be binding on something and moving suddenly after some pressure has built up.

Cheers

Dave

 

[Monkey Mark]

I laugh at folks who tell me they do this but it's their choice I guess:

Do you turn your TV/DVD/VCR/Sky box/boiler/hi-fi/kettle/oven etc etc etc off by the mains switch before going to bed?
The items don't have to be running for a fault to occur, so leaving items on standby can potentially be just as bad.
Yes the potential for greater damage to occur during the night may be present, but so are my smoke alarms just in case.

 

[doorframe]

NoLegs, it's an open vent above the house roof.

Deejay, I can get SWIMBO to do a rinse only, Although I can't see it being a heat issue, I can run away a sink full of near boiling water (through the same waste pipes) and see what happens. But, running away a full bath of hot water does not reproduce the noise.

Woodpig, scary report in the Guardian! But like Phil, I'm on economy something.

 

[doorframe]

Well, when I got home from work I turned the isolator to less than 1/2 of it's 1/4 turn, and ran the d/w. After about 20 minutes.... bang, bang, bang, about 20 second apart, all from the soil stack. About 1 minute later, bang, bang, bang again. I cant tell what part of the program it's running, but it's definitely not filling.

It's driving me mad (hammer)

 

[n0legs]

NoLegs, it's an open vent above the house roof.
.

Is the vent clear/open?
If the soil system can't "breathe" it may be the cause of your noise.