Dishwasher or pipe issue

[Texas Proud]

OK, this one has me stumped..... looking for some help...

A few weeks ago we had our water pipes knock very badly in the walls... it sounded like they were knocking all over the house...

I have determined that it is the dishwasher that is the cause... when it happens, I can turn on almost any faucet in the house and it will go away or be reduced significantly.... The water that is coming out of the faucet is a stream, but you can tell that it is pulsing...

I think there is supposed to be some kind of hammer prevention built into the pipes that traps air, so I drained the pipes to see if that might be the issue... NOPE... still have the problem...

Tonight when it happened, I looked under the sink and you can see the pipes moving... but the worst sound is coming from the bathroom on the other side of the house....


SOOOO, anybody have any suggestions of what can be causing this and how to get it fixed

[samclem]

"Water hammering" occurs when valve closes very rapidly (like an automated valve on a dishwasher or washing machine can do) and the fast-moving column of supply water slams into the closed valve setting up a pressure wave that goes back and forth inside the pipes. It can be destructive. There are "hammer arrestors" that can prevent this problem, they help absorb the pulse of fast moving water. They can fail if the air chamber inside them fills with water. The water can be emptied, but I'm not sure if just letting the water out of your house plumbing will do the trick.

You could pull out your dishwasher and see if a hammer arrestor is installed there, or it might be under the sink where the dishwasher supply water branches off.

Here are some models of hammer arrestors. They are available in regular hardware and plumbing stores.

I don't have any of these in my house and I don't have any problems with water hammering. I think a lot depends on the particular configuration of the pipes, how quickly the valve closes, water pressure, etc.

[dmpi]

Same thing happened to me a few years ago. After chasing the problems for weeks. Even draining my whole system I realized that all I had to do is lower the water pressure of a bit. You can do that by turning the water cut off valves under the sink a bit (quarter turn or so). However I can't remember if it was the hot or cold water. I think it was the hot water.

[Telly]

T/P, draining the system down was a good thing to try. IF there indeed are air columns in your plumbing system.

I built a house years ago where I put air columns at every faucet and appliance rough-in.

A house WITHOUT air columns - For example, if a water pipe (I'm using copper in the example) was run up a wall to a sink, the non-column method would be to solder on a 90 degree elbow at the top of the pipe, and then a stub of pipe out horizontally. Later after drywall and sink unit were installed, a shut-off valve for the fixture would go onto that stub.

A house WITH air columns - When the pipe comes upwards, instead of a 90 degree elbow, a Tee is used such that the stub can come out horizontally as before. In addition, a length of pipe minimum 18" long with a cap on the top end is soldered onto the top of the Tee. So that vertical capped length of pipe above the Tee has the air column in it, as there is no water flow through it. The water will compress the air in the column until it balances the water pressure at that moment. When a faucet or valve turns off quickly, the mass of water wants to continue, which will compress the air further, but then the water stops moving, and the air pressure forces the water down to equilibrium again. So the air in the pipe column acts as if it were a spring, absorbing the shock. Technically, it is an accumulator.

Eventually, however, the air absorbs into the water, which means the whole column becomes water-filled, so draining the system down will refill it with air. Trouble is, unless you are ripping things apart in a big re-do, you don't really know if your house has air columns. The house I am in now does not.

Dishwasher - we assume that the oscillation occurrs ONLY when the dishwasher is filling? They also fill when they are doing a rinse, so the spray arm/pump motor is turning then too.

If it only occurs when the diswater is filling, and this problem is new, I would pull the dishwasher's fill valve and see if there is crud in it. Most of the electrically-controlled water valves for appliances have an internal port that helps use water pressure to hold them closed. If crud gets in, maybe it is affecting its proper operation. Probably wouldn't be too expensive to just replace the fill valve either. Sears parts on their website is a good place for drawings and parts. If there is a Sears Parts warehouse in your area, they may have it in stock and just pick it up there, that is what I do.

[Brett_Cameron]

I had similar problem once. A toilet fill valve was weak and caused a pulsation when water was used in another part of the house. Try replacing the fill valve in the toilet in the bathroom on the other side of the house.

[JOHNNIE36]

A few years back we lived in a manufactured home community and had this problem of water/air slamming in the pipes. In our case it was caused by bad plumbing and valves in the community water system. My neighbor friend told me to drain some water to let the air escape that got trapped in the lines. This was done by letting an outside faucet run for awhile. So, you could water some plants outside while you are venting the system. Worked for me.

[Texas Proud]

Thanks for the info....

After reading up on this myself, I think it is the dishwasher fill valve... it happens twice during a dishwasher cycle... and it happens for a good amount of time, not just one bang....

If this is it, then the valve is opening and closing about 3 times a second would be my guess on seeing the pulses...

Now, I have to see how easy it is to get to it.... my wife is not that patient if I say I will fix it...

[Brett_Cameron]

Quote: "If a man says he will do something, he will do it! A woman does not have to keep reminding him every six months."

[JOHNNIE36]

That saying was made for my wife.

[glippy]

I'd check for poltergeists before going any further.

[Telly]

Will there be water all over the kitchen floor soon?

No really, getting to the fill valve on dishwashers usually isn't too bad, unless it is a tall-tub model. When I remodeled the kitchen, I put in a tall-tub type. That may be all they make anymore, I don't know. Making the tub taller means reducing the space underneath for motor, pump, wiring and hoses, etc. They are a pain to install, as there is no room to reach under to easily route stuff and position said stuff as you work it back into place. And as a tall person, I have come to dislike how far I have to bend over to put things in the lower rack, or to pull out the lower rack. That few inches lower of the tall-tub really makes a difference to me.

[Texas Proud]

Quote:

Originally Posted by Telly Will there be water all over the kitchen floor soon? No really, getting to the fill valve on dishwashers usually isn't too bad, unless it is a tall-tub model. When I remodeled the kitchen, I put in a tall-tub type. That may be all they make anymore, I don't know. Making the tub taller means reducing the space underneath for motor, pump, wiring and hoses, etc. They are a pain to install, as there is no room to reach under to easily route stuff and position said stuff as you work it back into place. And as a tall person, I have come to dislike how far I have to bend over to put things in the lower rack, or to pull out the lower rack. That few inches lower of the tall-tub really makes a difference to me.

Yes, there will be water all over the house if it keeps going like it is.... we are talking some BIG bangs of the pipe.... and I bet they have been weakened by my local utility district....

Our neighbor just had all of their pipes replaced due to the utility district using some chemical (I do not know what they used)... it seems to be bad for certain pipes... my sister that lives close by said her neighbor also had to change out his pipes... he lives in a different utility district, so it seems it was something that was being pushed at the time... I understand they no longer use it, but some people did not have great pipes to begin with and had to shell out $10K to fix them...

We might have a tall tube like you say... the bottom seems to be lower than my older unit.... I have not taken it out to look.... I do not see any electrical switch for it, so I would have to figure out which fuse it is on.... my wife seem to prefer paying Sears to fix it 'just in case'....

[Texas Proud]

OK... an update....

I decided to have someone take a look at it just in case I was wrong...

They came and had not had this happen before... called their boss to get directions... they tested the volts going to the pump and measured 102... so they were thinking something else was wrong... he checked other things and kept going back to the pump.... he did not want to pull it out to check the volts going to the dishwasher, so checked a wall socket...

So here is the interesting thing.... he did not get a reading... so pulled out an analog volt meter.... and also did not get a reading... I happened to have mine out so I brought him mine... 126 from the socket.... so he hooked mine up to the pump and got 126.... this was after one hour of fiddling....

I think they finally decided it was the pump and had to order one.... it will be delivered the middle of next week.... cost of the pump about $60... cost for the service call and coming back to put it in... about $130..... overall, not that bad...

The best part (when it is finally fixed).... the wife will be happy.....

[Telly]

Pump? What pump?

About not measuring voltage - Many meter probes are chubby enough at their ends that when inserted into a wall outlet, the outer diameter of the probe tips hits the sides of the outlet's insulator, and what little probe tip is beyond doesn't hit any metal. Going in at an angle can help. Of course, sticking two paper clips into the outlet works the best. BZZZTTTT!

[Texas Proud]

Quote:

Originally Posted by Telly Pump? What pump? About not measuring voltage - Many meter probes are chubby enough at their ends that when inserted into a wall outlet, the outer diameter of the probe tips hits the sides of the outlet's insulator, and what little probe tip is beyond doesn't hit any metal. Going in at an angle can help. Of course, sticking two paper clips into the outlet works the best. BZZZTTTT!

Sorry..... water inlet valve....

[travelover]

Quote:

Originally Posted by Texas Proud Sorry..... water inlet valve....

That makes more sense. My dishwasher was groaning and I finally traced to to a mostly plugged screen in the inlet valve.