Simple sewer hookup question

WayneW

New-to-us barely used 2021 320S Boondock.  We had a TaG Boondock XL that we loved but figured it's time to make the next, and hopefully last move up.

We have a shakedown trip coming up soon for 3 nights at Hell's Gate State Park in Lewiston, Idaho, the lowest elevation in Idaho (710 ft), fairly warm, and fairly close to home.  We inadvertently reserved a campsite with full hookups.  This might work well for us because the trailer is still winterized and I can do the flush there.  The guy who winterized it filled the Alde tank with antifreeze so I need to do the full flush.  I have the ability to store the trailer in a garage at home so if I de-winterize now it will be good for the year.

I've never had a trailer with any kind of a sewer system and we mostly boondock anyway.  So, my question.  Once I run the hose from the gray water tank (no black water because of the cassette toilet), do I leave the dump valve open all the time or do I drain the tank, close the valve and wait until the gray water tank fills up a bit to drain again?  Is there any risk of sewer gas/fumes backing up into the tank and trailer if I leave the dump valve open?  I know, a real rookie question, but tents and TaGs don't have sewer hoses to worry about.

Thanks, and we're looking forward to enjoying our new trailer.  Lots of good information here!

4ncar

Welcome to the world of "standup to dress!" 🤓

Since you do not have the black tank, you can leave the gray tank waste gate open.  If you had the blank tank, you wouldn't want to leave it open because you would use the gray water to flush the hose after dumping the black tank.

I can not think of any other reason that you can't leave the gray open to drain as you use.

Good luck and have a good time!

CrabTab

My thought would be to leave the gate closed until time to dump because any solids that went down the sink drain would have more fluid to flush them out of the gray tank... but I have been proven wrong before.😎

bergger

Yes I agree with leaving it closed.  I always leave ours closed until its time to empty it.  Less likely to have stuff caught in your sewer hose or left in the gray tank.  

falcon1970

Leave it closed until you want to dump.  If you leave it open you are leaving a direct line from the sewer into your trailer for gases to enter.

Sharon_is_SAM

@WayneW - don’t forget to sanitize your plumbing after you dewinterize.  

Denny16

I leave the gate valve open whilst showering, this is the biggest dump of water into the tank, and close it afterwards.  At first we just left the tank valve closed, but after two,showers, we had a full tank baking up into the shower!  We do save the last shower to feed,use after dumping the black tank.  But since you have a cassette toilet, that will not be an issue for you. 

 

As for sewer gases getting into the trailer, that is what you have PTraps for, they prevent gas from backing into the living area, as the holding tanks are vented outside on the trailer roof.  In any case, I would normally leave the dump valve closed.
cheers

falcon1970

@Denny16  I'm probably in error here but I don't think there is a p-trap between the shower drain and the gray tank.  Does anyone here know for sure?
In any case, p-traps dry out with  almost no provocation.  Seems easier to leave the gate valve closed until you want to dump the tank and then close it afterwards.  Although your practice during showers sounds reasonable to me.

Denny16

Yes, there is a PTrap on the shower in the 400, and no doubt one in the 320 as well.  You can see the PTrap under the shower in the 400:when you remove the access panel under the shower/washroom door.  nüCamp cut a hole in the floor for it to drop down into.  Someone posted a photo of this in one of the threads on rodent proofing the TaB.  The new 320 might have a Hepvo valve in place of the PTrap, which is better.

@falcon1970, You are correct that P Traps will dry out if not used for extended periods, and this takes at least a week or longer, depending on humidity and temperature, not likely to happen whist camping and using the trailer.  Water can be sloshed out of the traps also by going down the road.  So I would run water in the sink and shower to refill the traps. 

That said, the newer TaBs are using Hepvo valves instead of P Traps, as they do not use water to form a seal, no drying out, no water or gas backups, and are a much better option all round.  I replaced the PTrap in the galley sink with a Hepvo valve, do not have a washroom sink, so no PTrap there.  Trying to work,out if I can replace the shower PTrap with a Hepvo valve?
cheers

Verna

It depends on the year of your T@B whether Hepvo valves or p-traps are used. 

My 2019 400 came with a p-trap under the kitchen sink and @Dalehelman was kind enough to change mine to a Hepvo to save room under the sink. But, my 400 also came with a Hepvo valve under the shower floor, not a p-trap. 

My 2021 T@B 320 came with a Hepvo valve under the kitchen sink. I haven’t had a reason to investigate whether my shower has a Hepvo valve or not. 

Denny16

Interesting Verna, our 2018 has a PTrap in shower and galley.  I saw some 2020 TaB 400 build photos with a Hepvo under the galley sink.  This is what gave me the idea to add one to my 2018.  

Cheers

jkjenn

One of the reasons to keep the gate closed is because odor can travel from the sewer up into the camper.

4ncar

falcon1970 said:

Leave it closed until you want to dump.  If you leave it open you are leaving a direct line from the sewer into your trailer for gases to enter.

That’s what the ptrap is for...

4ncar

jkjenn said:

One of the reasons to keep the gate closed is because odor can travel from the sewer up into the camper.

Ptrap( or hepvo) prevents that.