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post #5 of Old 07-14-2019
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Location: The house is in Kingsport, TN. Boats are on Watauga Lake and in New Bern, NC
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Re: GROCO K-type marine head question

When we are living on the boat, especially in the Bahamas where the water is saturated in calcium carbonate / calcium bicarbonate, we have a gradual buildup of a tan to beige mineral deposit in the Groco Type K bowl especially around the discharge. I clear it by adding an acid from time to time. Originally, I used a cup or two of diluted muriatic acid (35% HCl diluted to 10% HCl) every week or so as recommended by Bruce Van Sant. More recently, I have used a 1 oz scoop of citric acid powder (which I buy from Amazon in 5 lb bags) to the water in the bowl. Both remove the scale, and in use both fizz and stink of hydrogen sulfide. Beside the scale in the bowl which I can see, they also remove the similar scale that builds up on the joker valve. My valve does not seal when there is scale on it. It also must have its slit perpendicular to the two bolts in the flange that contains it in order to seal reliably. Even with periodic cleaning, the joker valves only have a life of two years or so; then they must be replaced. When the joker valve does not seal completely, the quart or so of "water" standing in the discharge hose rising toward the anti-siphon valve after flushing leaks back into the head partially filling the bowl.

I changed to citric acid as I am more comfortable with 5 lb of it on board rather than a gallon of muriatic acid. And, I am treating my holding tank with 1 oz citric acid and 1 or 2 oz of sodium nitrate after every pump out. The citric acid removes the "lime" deposits and the nitrate seems to keep the holding tank stink under control for a few days.

Bill Murdoch
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