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Sewer Gas Backup


thomasgibbens

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Tom, you might want to check your Mechanical Vents or better yet change all of them to this one. The ones that Monaco installed are really the cheapest ones you can find, duh!

The ones that I installed are called Studor Mechanical Vent.

https://tinyurl.com/yb2sh4ot

The only one I have not changed as yet is the one behind the Splendide but I will tackle that project one day when I get bored. When we get sewer smells it is usually from not using the washer so occasionally I have to run some water to fill up the trap.

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If you have a washer/dryer make sure it has a P-trap and that there is water in the trap to stop the sewer gas. Also run all the sink faucets to make sure those traps have water in them. There are valves under the sinks (can't remember the name) that can go bad and allow sewer gas to enter the RV. I changed all of those just for good measure. They are available at Home Depot and Lowe's.

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20 hours ago, thomasgibbens said:

Is there an easy way to stop sewer gas from backing up in the coach?  I know I can close the valves and open only when the tanks are full but wondered if there was a back flow or trap that I can purchase. 
 

tom gibbens

15 Dynasty 

 

Sure enough, I found one under each sink and will replace them with the Home Depot model. Thanks, I’ll give it a try. 

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18 minutes ago, Grampy OG said:

Does the Studor Mechanical Vent replace the under-sink vents or go on the rooftop

Ken, they are located inside usually one at each sink and one behind the washer/dryer. They thread into the 1 1/2 PVC pipe which drain to the grey tank.

The roof does not use mechanical vents. They are open all the time or at least they are supposed to be.

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Thank you for the quick response. I was pretty sure we were talking under sink. I have replaced mine in the past with off the shelf much lower cost vents but I am going to check out your recommendation. Always good to keep good vacuum release on the sinks.

 

Thanks Ken

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Frank,

That works great for any odors that come from the sewer drop if you leave the valves open which I never do except if my wife or I decide to use the washer which would be a VERY rare occasion. However the Mechanical Vents inside the coach on every grey water sink drain accomplish two functions, one which allows the water to drain correctly but two, when they decide not to seal properly, the odors from the tank itself will backup into the coach.

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Tom:

If your main concern is sewer gas from the sewer at your campsite, then you're probably leaving your dump valve(s) open.

I wouldn't personally leave the black tank valve open.  Doing so lets the poop land and stick to the bottom of the black tank.  I think it's prudent to start the black tank with a few gallons of water, let it fill naturally and then when it's sufficiently full or annoyingly stinky, dump it.

Leaving the grey tank dump valve open could be OK, but if your grey tank is empty when you dump the black tank you lose the chance to flush the black tank residue out of the dump hose with the grey water.

Dwight

 

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Interesting. I don't have any smell when I'm stopped, but when I drive down the road, I can smell it all the way up front. Not bad, but I have a good nose. Others riding don't seem to pick up the scent.  Don't know where it's coming from either. The Bathroom smells just fine. Sinks too. Suggestions?

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I had a similar issue at time when headed down the road. First I confirmed that my vent pipe was attached properly and then I ran a hose down it to be sure it was not blocked. With both of those things confirmed I decided to try the “Cyclone” roof vent and it completely solved my problem. Have not had even the slightest smell since. 

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1 hour ago, Chargerman said:

I had a similar issue at time when headed down the road. First I confirmed that my vent pipe was attached properly and then I ran a hose down it to be sure it was not blocked. With both of those things confirmed I decided to try the “Cyclone” roof vent and it completely solved my problem. Have not had even the slightest smell since. 

Thanks, I see they range from $15 to $40. Does the brand or price matter?

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I’m a little late here, but I found that these vents work the best going down the road for the price, at a little under $5.00 each.   If you compare them to the ones at most of the box stores, the ones in the stores don’t have a spring in there, and eventually the rubber gets old and they sag and leak.
 

After much research and searching I found them at www.cpesupply.com

 

My 05 Dynasty has 5 of these guys hidden in places, 3 under sinks, one behind the washer/dryer, and one behind one of the kitchen cabinets for the shower.

Don’t forget to add a little Teflon tape to the threads when you replace them.

When I have odors now, I’m pretty sure it’s a empty trap.

0D402D5D-8247-44E3-9FBA-9C33D2A9C52F.jpeg.2f3dcd64a7f4abe5dfb8e7abef2b021c.jpeg

 

 

 

 

760424E9-7A29-4465-89B6-81598E164F14.jpeg

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We fought sewer smell for several years on our new to us 06 Monaco Dip. Replaced air admittance valves twice with little success. Finally found roof vent pipe extended too high above roof and original rain cap effectively sealed it. Trimmed pipe and installed 360 venturi cap. Big improvement, but only issue. 

When replacing the water heater I discovered the ABS pipe on the top of the black tank had a hairline crack a the junction of tank/pipe. A little more improvement. 

I'm going to look at the mechanical air admittance valves and a different roof vent valve. 

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We have the same problems at times, not always though.  Replaced all the under sink valves, didn't help.  Someone suggest checking the connection of tank and vent stack.  There could be a broken seal there that allows gas into the coach as the tank fills or empties and the size of the tank changes a little.  Have not gone to all the work to get to these tank/stack connections yet.  If it looks like that might be the problem, I think I'll try some caulking called "big stretch" to reseal.

Woody Miller

09 Dynasty Regal IV

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19 hours ago, mrktrain said:

Short of deconstructing my PDQ Diplomat, is there anyway I can determine the routing of the holding tank vent stack? I want to check for loose connections. 

Ken,

Open the passenger side cover behind the water heater. There are straps under neath that need to be removed and then the door swings up. The black tank vent pipe does not make a straight shot to the roof and there are elbows somewhere behind the washer/dryer. My memory is foggy on that. Here is a photo to help you locate the vent pipe.

929845973_Tankaccessoncurbside.jpg.ca021a9be34e46bca84e8548e15df4c8.jpg

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3 hours ago, mrktrain said:

Bob, that's the connection I resealed with Flex seal - the stuff the TV guy patched the bottom of a boat with - and it helped, but didn't completely solve the problem. I'm assuming the gray tank is also vented,. Any idea how/where it is vented? 

 

Ken the gray tank is vented in the same area and connects to the same up pipe that travels to the roof for the black tank. The gray vent comes out of the tank and goes vertical until it reaches the horizontal pipe chase in the bathroom and then there is a right angle elbow changing the direction over to where it tees into the black tank up pipe in the vertical pipe chase in the bathroom. If you look near the outside wall above the washer/dryer you can see the vertical pipe as it travels to the roof.

 

Pipe chase in bathroom.jpg

Tank access on curb side.jpg

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On 9/8/2020 at 2:38 PM, Dwight Lindsey said:

Tom:

snip/

Leaving the grey tank dump valve open could be OK, but if your grey tank is empty when you dump the black tank you lose the chance to flush the black tank residue out of the dump hose with the grey water.

Dwight

 

I leave the grey open/black closed if parked for several days.  To avoid what Dwight refers to, I close the grey the night before we leave. That way, after two showers, the grey has enough hot/warm soapy water to flush the black when I dump. Never have had any smell in 12 yrs full timing...Dennis

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