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Vacuum Head Pump

Discussion in 'Cabo Yacht' started by CSkipR, Dec 22, 2013.

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  1. CSkipR

    CSkipR Member

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    On one toilet it will run every 10 minutes. Vacuum pump kicks on. I have checked all fittings and clamps and are seem to be tight. Called Dometic and they recommend replacing the vacuum pump (385310540). Looking at the pump there is not much too it. Can it just be adjusted or is there something inside that I am missing?
  2. Pascal

    Pascal Senior Member

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    Replacing the pump?? That s a joke, right? All you have to replace are the duckbills (2 at the inlet and 2 at the outlet). Takes 10 minutes... They usually last 5 to 8 years

    Flush a lot of water first then remove the hoses and fittings in each side of the pump Clean the fittings and instal new ones. Put some liquid soap on the DB flanges so they don't twist when screwed in. Don't over tighten
  3. Capt J

    Capt J Senior Member

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    As long as the bowl is holding water, this is what you need to do. Use a heat gun to heat up the sanitation hose to get them off and on. The duckbills come in 2 sizes 1.5" and 2", your are most likely the 1.5". I always keep a spare set on board.
  4. Pascal

    Pascal Senior Member

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    Yes indeed... If water doesn't stay in the bowl then it s the bowl seal not the DBs. Often scrubbing the edge with bowl will solve that problem
  5. CSkipR

    CSkipR Member

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    Replacing vacuum pump switch

    I should have mentioned I changed the duckbills a few months ago to see if that would fix the problem. It did not. The one toilet vacuum pump kicks on every 10-15 minutes and the toilet is not loosing any water out of bowl. The tech at Dometic recommended changing the vacuum pump switch which is approx. $140.
  6. Pascal

    Pascal Senior Member

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    Yeah you could have a leak t the switch membrane but you should be able to hear it. Turn off everything on the boat incl air cons and you should hear the leak if at the switch. Try wiggling the switch shaft around and see if it makes noise.

    It still may be worth reinstalling the DBs. Sometimes they get twisted. Make sure the flanges are clean and scrape up calcium deposits, then lube with liquid soaps before re installing.

    What do you have, vacuum generators with the pump mounted on top or stand alone bullet shape vac tanks? If the vac gen, check for vac leaks at the fittings at the pump inlet, the PVC dip tube
  7. CSkipR

    CSkipR Member

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    Vacuum generator with pump mounted on top. I just tried letting it pump up and then turned pump off and waited 20 minutes. it still had a lot of vacuum. So based on previous comments it appears to be the vacuum switch. Will listen and see if I can hear anything.
  8. Capt Ralph

    Capt Ralph Senior Member

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    Had a ship with a crack in one of the bullet shaped reservoirs. Took a while but I found it. Looked like it was dropped before installation.
    The Dometic hose nipples do not have barbed ends, usually the hose slips off easily & heat guns are not required.
    My managed boats get new base gaskets and DBs every 2 years, working fine or not.
    I keep a generous supply of spares on hand.
  9. CSkipR

    CSkipR Member

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    Pictures of switch

    Attached Files:

  10. Capt Ralph

    Capt Ralph Senior Member

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    Cleaning/replacing the O rings can offer the same results and bux cheaper.
    Before you jump on the switch wagon, the duck bills have been recently (correctly) replaced?
    Two systems? Rotate the switch assembles between the systems and see where the problem goes.
  11. CSkipR

    CSkipR Member

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    Yes duckbills were changed a couple of months ago. I do have two heads although the other head pump is more difficult to get to I may give that a try. Good idea.
  12. Capt J

    Capt J Senior Member

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    I've had to replace those switches before and have had them go bad. Given the year of your vessel it's probably about time to change the switch. Try wiggling or tapping the switch a little and see if that causes the pump to come on.

    Also, the pump is only held down with 4 screws, so sometimes it's easier to just unsecure the pump assembly and move it to an easier place to work on it.
  13. d_meister

    d_meister Senior Member

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    One common problem with the systems is the hose installation. Although the hoses often need to be heated to install and remove, the hose clamps should not be tightened until the hose has completely cooled. Tightening the clamps while the hose is soft will often times damage the hose, causing a leak.
    Otherwise, a commonly overlooked source of air leaking into the closed system is the flush ball valve axle. Over time, the shaft can wear and the "O" rings on the shaft can wear out. Earlier flush shafts were plastic and wore excessively, The replacements are brass. A simple test to see if there is a vacuum leak at the axle is to lift the flush pedal slightly to center the shaft in the pedestal journal after flushing. If the cycle frequency changes significantly, then that is the problem area. You can try just replacing the "O" rings on the shaft, and be sure to grease the parts well with a good silicone type of grease, including the top of the water valve where the pedal pushes down on it and also the ring of the pedal that fits around the spring assembly. The pedal can drag on those bits and not return fully.
  14. CSkipR

    CSkipR Member

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    d_meister,
    I sent you a PM.
    Skip
  15. CSkipR

    CSkipR Member

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    706 Dometic Toilet

    Okay I'm winding down on ideas. Definitely now know its not the vacuum pump as I switched the two in the boat and the problem remained at problem head.
    Decided to take the flush section apart and did not find any o rings on the brass piece that pushes down. I looked it up this one does not have o rings. Actually everything looked good so greased and replaced. I do need to replace the flushing bar as it hangs up if you push the lever to far down. Only thing I have not been able to check is the vacuum breaker on the back of the head. It is difficult to get to without removing the toilet although I was able to check the hose clamp. Its funny it now kicks on about every 15-18 min whereas the other day it was kicking on every 12 minutes.
  16. Capt J

    Capt J Senior Member

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    If the pedal assembly goes too far and hangs up, it's in the pedal assembly and that's where your leak is. The rod gets bent when it's pressed too far one time and then it starts leaking there......I had to replace one because of that.
  17. CSkipR

    CSkipR Member

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    Capt J,
    Okay will order a new assembly and also the pedal rod. I took the assembly apart and it all looks fine. That is the part that has the plastic head that fits on top of the brass rod with the water connection and vacuum line.
    Thx, Skip