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MilesandSmiles's avatar
MilesandSmiles
Explorer
Jan 07, 2018

2004 Southwind Black Tank Flush doesn't work

This morning I tried to use the built in Santi Flush black tank flushing system, which has worked in the past. Today it seems to be blocked and water will not flow through the system at all.

Yes, the black tank drain valve was open.

I've heard some people say that there's a check valve somewhere that can get jammed. Can anyone tell me where to look for it on my coach, and what it will look like if I find it?

Any other suggestions as to why the water won't flow into the black tank from the hose?

Thanks
Class A
  • Artum_Snowbird's avatar
    Artum_Snowbird
    Explorer
    Jan 07, 2018
    The check valve is usually just behind where you screw on the hose. Under the three screws holding the plate on, and you will see it. It's about 3/4 of an inch long and normally prevents water from flowing out of the system water supply. I suppose that can get stuck. Push on the center button when there is no pressure in the system and you should feel it go in and come back out under spring pressure only.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Jan 07, 2018
    More likely the holes on head inside the tank are plugged...remove and drill larger holes.
  • dalenoel's avatar
    dalenoel
    Explorer II
    Jan 07, 2018
    Had the back flush blocked on the new-to-me Monaco and it was plugged in the nozzles in the black tank. Took it off and drilled out slightly larger holes after cleaning all crud off the unit. Sprays very well now and not a problem. One less to worry about.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Jan 07, 2018
    Whether black tank drain valve is open or not has no bearing on whether water can flow thru flush system
    Having the dump valve open while using the flush system is 'JUST In CASE' preventative measure....get distracted and water continues to flow in until tank is FULL the OVER FULL ----blowing past toilet bowl seal OR worst Blowing out tank vent on top of RV


    The hose connection MAY have a check valve inside it....like the city water connection.
    Most don't so water can flow back out after disconnecting hose

    The other 'check valve' is actually installed high up typically inside the bathroom cabinet or even a closet.
    It is an 'anti-siphon vacuum breaker' on the inlet line.

    Some times that can fail...usually you will have water flowing out of open top when that happens.


    More typical when there is not flow (and as worked OK in past) is the nozzle in tank has become clogged.

    Some nozzles can be removed and the holes in nozzle cleaned....depends on installation used,
    *Nozzle glued in place
    *Nozzle held in place with screws
    *Nozzle spun welded in place (spun at high speed creating heat that melts tank wall & nozzle flange together)




    Anti-siphon Vacuum Breaker
    Several versions.....Black/Cheap junk to Brass/better quality




  • STBRetired's avatar
    STBRetired
    Explorer
    Jan 07, 2018
    On my MH there is an anti-backflow valve attached to the vacuum break up under the bathroom sink as pictured in the post above. Whenever I have had issues with my rinser, it has always been something stuck on the sprayer, never with the check valve or vacuum break.

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