Groaning noise while using black tank flush

36ckts · 10-02-2019, 07:17 AM

Ok folks lets hear some possibilities. When using black tank flush there is a groaning noise when I have the water flowing to it. Anyone ever heard of this issue? Seems to be flushing but there is very little water coming out while doing so

**Flybob** · 10-02-2019, 07:31 AM

Could be an issue with the backflow valve restricting the water flow. Is the water pressure good?

NJKris · 10-02-2019, 07:58 AM

Mine makes groaning noises too, but water is definitely going into black tank. Check the hose going into the black tank underneath your trailer, during my PDI I discovered the hose run was too short to make the bend, and it was badly kinked. The dealer fixed it by putting hose clamps over the kinked area to squeeze it round.

The Evil Twin · 10-02-2019, 08:11 AM

Mine does it. I thought it was normal.

I have not traced out the line but I assumed it was the BFP. There is no shortage of flow to the tank judging by what it breaks loose in there.

**Bama Rambler** · 10-02-2019, 08:19 AM

Some black tank flushes are 'Tornado' style where the head spins when it's flushing and they'll buzz or hum when running.

Looks like you have a Cedar Creek 36CKTS, but you don't say what year it is in your signature or profile so I don't know if it was installed at the factory or was an add-on.

36ckts · 10-02-2019, 09:08 AM

It's a 2014 CKTS and it's factory installed

aknavy · 10-02-2019, 09:08 AM

I have the factory flush, and I also get a groaning sound. No kink in the hose or issues routing issues. I did, at one point, have the flush clog. I took it apart and enlarged the pin holes that it uses to spray the tank, re-installed, and there is less groaning now. Now, I mostly hear water splashing on the side of the tank.

NJKris · 10-02-2019, 09:09 AM

Evil Twin, based on your Avatar, I think you were following me pretty close on the Tail of the Dragon! Let you pass and then tried to keep up with you.....nope.... lol.

36ckts · 10-02-2019, 09:18 AM

I wondered about it being clogged. I had one on my Sandpiper years ago that was an add on and it clogged. That was fun getting to. I'm guessing I'll need to pull the under belly to get to it.

The Evil Twin · 10-02-2019, 10:36 AM

Quote:

Originally Posted by NJKris

Evil Twin, based on your Avatar, I think you were following me pretty close on the Tail of the Dragon! Let you pass and then tried to keep up with you.....nope.... lol.

LOL, at the Tail it would have been on the "Moose". The bike in my avatar is race only. If you ever go to NJMP in Millville you'd see it

This is the street bike:

NJKris · 10-02-2019, 11:05 AM

I"m always happy to see bikers 'taking a knee' on the Tail. I groan when I get stuck behind regular bikes that can't go faster than my Corvette!

plymaniac · 10-02-2019, 01:35 PM

I have a 2015 Cedar Creek Silverback. It makes a loud humming noise while the black tank flush is operating. I guess it could be called a groan.

I always attributed it to the anti-siphon valve and took it as a sign that everything was working properly. The valve was originally installed backwards at the factory and never made a sound when I tried to flush. But it wasn't allowing the water to pass through to the black tank either.

I think you're OK if the results of the flush are satisfactory and there are no leaks.

jeff_s · 10-02-2019, 04:19 PM

If very little water is coming out I would first look at the Check valve/vacuum breaker. It's usually a lot easier to get to than the spray head in the tank itself.

I had the same problem a few months ago and replaced the plastic valve with a brass check valve.....problem solved. Much more water now and better flushing action. See picture of the check valve I installed. I also have a new brass vacuum breaker but haven't installed it yet.
Jeff

CGK · 10-02-2019, 05:01 PM

We also get the "groaning" noise when we flush; and there is plenty of water going into the tank, judging from the amount of water flowing out of the tank while we are doing the blackwater flush (we use a clear elbow so I can see the results of my labor). So the noise and reduced water flow may not be related in any way, based upon our experience with the last two TTs.

TitanMike · 10-02-2019, 05:38 PM

Based on my experience over the years with "groaning" in water pipes, it comes from low flow and a valve that has a loose stem or washer. In the case of the tank flush the back flow valve might be causing the groaning because of a restriction downstream. Not enough water is flowing to keep the valve completely open and the internal spring is causing the valve mechanism to "flutter".

Just like the water faucet that "groans", it will go away if more water can pass through.

If there is a poll on what might be the cause my vote goes to a restriction in the form of a kink in the lines between anti-siphon/back flow preventer/check valve and tank. Could also be plugged orifices in the actual flush head itself.

Needs more water flow to hold the check valve more wide open.

plymaniac · 10-02-2019, 08:13 PM

To the original poster,

I overlooked your statement that very little water was coming out of the black water tank during the flush. That may change my earlier comment that all may be well even with the groaning sound.

Assuming a typical water hook-up, if your flush outflow is just a trickle it's either a bad anti-siphon valve, clogged or broken spray nozzles or a kinked water supply line. You should be able to trace the water supply line from the city connection to the anti-siphon valve to find any kinks. The valve is easily replaced if you can work with Pex fittings. Bad spray nozzles are too big and dirty of a project for my pay grade.

All that being said, when I first operated my black water flush system I was surprised at how little water output there actually was during a flush. But I could see solids being removed. The outflow is much less than a normal gravity-fed tank dump. The diameter of the water supply line is just not big enough to produce a bigger flow.

I run my flush for an hour or more until the outflow is crystal clear. Where I camp the water doesn't cost me a thing.

Good luck. You will solve this problem.

TitanMike · 10-02-2019, 10:28 PM

Quote:

Originally Posted by plymaniac

I run my flush for an hour or more until the outflow is crystal clear. Where I camp the water doesn't cost me a thing.

Wow, I thought I was flushing my tank for a long time when I let the flush run for 10 minutes.

Arnie M · 10-03-2019, 01:14 AM

Quote:

Originally Posted by 36ckts

Ok folks lets hear some possibilities. When using black tank flush there is a groaning noise when I have the water flowing to it. Anyone ever heard of this issue? Seems to be flushing but there is very little water coming out while doing so

You are lucky to hear a groaning noise.
My first attempt flushing our tank did not go so well. The black flush check valve was installed backwards. Swung the valve to the correct flow path and still did not work. Took the check valve apart and removed the ball for a flush. Made my own black flush check valve until end of season then took the RV back to dealership for this and other repairs.
Flush is working well now.
The sound I hear is water spraying into tank. Suspect I only have nozzles and not twirlers.

Chris Pastuzyn · 10-03-2019, 04:47 AM

Had the same issue on my 2511s, traced it back to the spring on the backflow preventer, was able to get it to work by playing around with the spring but I'm going to replace it, The spring is way to stiff. IMO

markb422 · 10-03-2019, 08:26 AM

Hydraulic check valves and relief valves make a groaning noise.

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