380FL Rear Bathroom Plumbing

[bpage1124]

I'm having a big problem with the rear bathroom plumbing. It doesn't matter whether the black tank is empty or not when you open the flush valve the waste always seems to be close to the top and will not drain. I'm told it is a design flaw and I'm wondering what I can do to fix the issue.

[JBill9694]

Welcome to the forum. A little confused on exactly what the problem is so might need more information.

You state that even when the black tank is drained the waste water is close to the top and will not drain. Is the black tank not draining? If not this would indicate a plug in the line that needs to be removed by flushing. There are attachments for the end of the sewer line that will let you back flush without making a big mess on the ground (I recommend this method), or you can go in through the toilet but be careful not to flood your bathroom. Either way, make sure the drain valve is open before starting.

If the black tank is draining, but does so slowly then this would point to a ventilation problem, no air getting into the tank as it drains. A ventilation problem could also be the cause of the toilet flushing slowly or not at all. The black tank should have a roof top vent with a cap on it. Check and make sure that this cap is not crushed and is working properly.

Good luck, and please check out the welcome letter for new members; Welcome Letter to New Members - Grand Design Owners Forums (gdrvowners.com)

[TucsonJim]

I'm having a big problem with the rear bathroom plumbing. It doesn't matter whether the black tank is empty or not when you open the flush valve the waste always seems to be close to the top and will not drain. I'm told it is a design flaw and I'm wondering what I can do to fix the issue.

Good morning and welcome to the forum. Since this is your first post, I'm attaching a link to our welcome letter at the bottom of this response.

Let me see if I can understand a little better. When you say you "open the flush valve", are you referring to the drain dump handle and the waste you're seeing is in the drain pipe? If so, this is a pretty normal condition with many of the units. It's caused by minimal slopes for the liquid to exit the vehicle. But most of us have added an external dump valve to prevent any liquid from sloshing out before we hook up the sewer hose. To use the external valve, remove the sewer cap, attach the hose, open the newly added external valve, and then open the waste tank valve. Here's a link to the valve I'm talking about:

https://smile.amazon.com/Valterra-T5...s%2C225&sr=8-3

New member letter:
https://gdrvowners.com/forum/main-fo...to-new-members

Jim

[bpage1124]

Hi Jim, I'm sorry I was not more clear. I meant if I push the peddle on the toilet, the waste is just a few inches from the peddle value

[Country Campers]

Looking at the information that the Moderators have access to you might be able to see the toilet drain pipe from the storage underneath. It looks like the drain pipe has to make angle to get to the black tank. It also enters the black tank from the rear of the tank and not at the outlet like some of the other floor plans. This would lead me to believe that the solids may collect at the rear of the tank where they enter. Pre filling your tank with about 10 or 15 gallons of water would help your issue. This would give the solids something to dissolve in and not for a "mound". You may need to spray down thru the toilet to get this blockage taken care of , not going to be a fun job , and once that is flushed out and using the pre fill method you " should" not have any more issues. I do not think it is a design issue.

Brian

[JBill9694]

Hi Jim, I'm sorry I was not more clear. I meant if I push the peddle on the toilet, the waste is just a few inches from the peddle value

Some gentle, low pressure plunging might help shift the load before resorting to sticking a hose down the toilet. I agree with Country Campers in adding 10 to 15 gallons of water to the tank after draining, and also recommend using plenty of water when flushing solids down the toilet. While there are those who believe it is not necessary, consider using a chemical additive to the tank to speed up the brake down of solids.

Another thing to consider is that the spray nozzles for flushing the tank are probably near the outlet valve since that is the critical area to keep clear, and will do little or nothing to clear solids from in front of the tank inlet, if it is at the opposite end of the tank as Brian suspects. Although the owner's manual will caution against this, you may be a candidate for repeated fill and draining of the tank to completely clean it. This would involve closing the outlet valve, filling the tank to near full with clean water, turning off the water, and then draining the tank. Repeat as necessary until discharge is clear. Some way to measure the water going into the tank is a must; flow gage, bucket, stopwatch. Valterra and Camco both have products that will accept a hose and will attach to the end of the drain line to make this process easier and mess free.

[Cate&Rob]

Part of this problem could be that the pipe from toilet to tank might have been pushed too far through the tank grommet during manufacturing. The pipe is supposed to stop at the ridge within the grommet, but it can quite easily be pushed beyond that. If this pipe is within an inch or two of the bottom of the tank, it would not take much of a mound (as discussed earlier) to block the flow.

Rob

[howson]

Hi Jim, I'm sorry I was not more clear. I meant if I push the peddle on the toilet, the waste is just a few inches from the peddle value

Did this get resolved?

I'm curious is Cate&Rob's input is the issue, or it's not enough water (as mentioned previously) or if debris from when the trailer was built is blocking the drain. (If the latter, getting it out will not be a fun job...)

Howard