8700 Dometic Master Flush Toilet won’t hold water

[April]

My 2017 Dutch Star 4369 mid bath won’t hold water after I flush. What needs to be replaced? Anti siphon valve, Duck Bill or something else I‘m missing? I have already replaced the macerator motor last year. Now this! Oh the joys of RVing!

 

[Neal]

Are you in low water mode by any chance? See 6.2.2 on page 7:

http://productimageserver.com/literature/ownersManual/56503OM.pdf

 

[April]

Oh no. It doesn't matter if its in low flush or full flush. Even when you add water it drains out. Thanks, I am very mechanical and not new to this, just want to replace the correct part. Thanks for your response .

 

[NWIP]

The height of the discharge loop is what controls the water level. If the loop is low water siphon out the bowl. Try and raise the top of the loop, use tie wraps to hold it higher if necessary. It doesn’t take much and had this problem after reassembling from pump change.

 

[April]

Will look at that again, but it worked fine for 8 months after pump change.
Thanks @NWIP

 

[Just George]

@April It has also been reported that the anti-siphon valve which is part of the discharge loop can get dirty and fail to close. Cleaning the valve by flowing a small amount of bleach and or dish soap along with a soft brushing in the valve openings has reportedly remedied the issue for some.

 

[April]

Thanks @ Someday Came