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  • Water from backflow preventer

     fixbear updated 3 months, 2 weeks ago 4 Members · 10 Posts
  • grasshopper

    Member
    June 1, 2021 at 5:04 pm

    I have a Hobart commercial dishwasher. Recently started flooding the kitchen. Coming from the backflow preventer. Why does it suddenly have water going backwards?

  • fixbear

    Member
    June 1, 2021 at 9:01 pm

    It's not going backwards, it's not closing during the rinse cycle. Common item. Caused by a build up is calcium. Remove the top and core. soak them in vinegar or other food grade acid to dissolve the minerals that are making it hang.

  • ectofix

    Member
    June 1, 2021 at 9:45 pm

    Are you talking about the vacuum breaker? (link provided only as an example. Yours might be identified by a different part number. That DOES matter.)

    Vacuum Breaker

    Those are the most common parts to fail on the Hobart dishwashers that we maintain. The simplest fix is to simply keep rebuild kits on hand.

    Hobart uses Watts vacuum breakers, which are very common and easily purchased aftermarket. But again, to keep it simple, just order the kit listed in your dishwasher's parts manual.

  • olivero

    Member
    June 2, 2021 at 12:01 pm

    Do you use any kind of rinse aide for the final rinse cycle?

  • grasshopper

    Member
    June 2, 2021 at 1:41 pm

    Thanks fixbear. Cleaned all up with vinegar, but still not working. Ectofix, yes, water coming from the vacuum breaker. Bought a replacement kit, and found they are supposed to have a spring. It does not come with a spring retainer and our old one doesn't even have a spring. Going to have to buy the whole vacuum breaker. Olivero, yes, I think there is a rinse aide. Never paid attention as I don't use it myself. Just a maintenance guy trying to save the business from a plumber fee.

    • olivero

      Member
      June 2, 2021 at 1:56 pm

      Okay, well, one thing I ran into on my Stero machine is the rinse aide was actually very corrosive, so the standard vacuum breaker on the rinse aide line would get eaten rather rapidly, I had to change it about once a year, the brass would just get eaten. It would also eat the copper pipe it was run in for about 1′ it would just eat through the elbow.

      I ended up replacing all of it with 316 S.S fittings and then speccing this guy https://www.statesupply.com/jo1015

      Which is a Kadant vacuum breaker, just screws in and it's all stainless 316, haven't had a single issue for the last 5 years.

      P/N is VB8-76-SS-T-S-E 3/4″

      That could also be why just cleaning it up isn't doing it, for me the rinse aide was the problem despite the chemical OEM saying it was “not corrosive” the pinholes in my copper told me otherwise.

      Nothing wrong with doing that, replacing it with the exact same one will be just fine for whatever duration it lasts, doesen't require a plumber I wouldn't think.

    • ectofix

      Member
      June 3, 2021 at 12:33 pm

      @grasshopper There is no spring and they don't come with one. It's simply water pressure that closes them an gravity that opens them.

  • fixbear

    Member
    June 2, 2021 at 3:15 pm

    Olivero, that sounds like electrolysis instead of corrosion. But I'm also surprised that the injection is upstream of the vacuum breaker. The purpose of it is for the protection of the domestic water system contamination. As is the incoming water check valve. I've had zoning inspectors check that in the past. Being the tap is often made by the chemical supply company installers.

    • olivero

      Member
      June 2, 2021 at 4:42 pm

      No, definetley corrosion.

      None of the other piping on the machine, which all come from the same main have had this problem.

      It's the rinse aide, it would eat through the elbows and be injected right after the vac breaker, so it would suck it up occaisonally, but it didn't take much.

      No doubt about it.

  • fixbear

    Member
    June 4, 2021 at 11:08 am

    @grasshopper, When you took it apart, did you check the seats to be smooth and verify that the guide post do not hang? This is a gravity valve that has to be plumb to work right. The moving valve part also uses air to help it float with the water rush in. You may also want to check the water inlet line screen before the solenoid valve for restriction. And check the water line pressure. If the water coming in does not come fast enough, and at the proper pressure, the valve will not seat. I've seen were a supply line got partially crushed from slamming racks under the drying table. You also want to check the rinse spray wands to have tight bearings and all of the nozzle's in place. We all tend to forget that other things may effect what we see as a problem.

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