07/10/2026
Struvite! "The Silent Killer"
OK, maybe a tad overly dramatic but the consequences may put a damper on that summer vacation quickly. Struvite, or Magnesium Ammonium Phosphate (MAP for short) crystallizes as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. Check out the photos in this post.
Struvite readily forms in alkaline conditions where its constituent ions are present. It forms readily in areas associated with organic matter decomposition — yes, like your black tank — and bacteria that react with urea. The pictures in the post are from some of the black tanks that I have cleaned. The customers complained of sensors not reading correctly (always high), slow or no flow when emptying tanks, reduced tank capacity, and foul odors. Sound or smell familiar? There's your clue.
One way to know if you have struvite is the appearance of a sandy or scaly substance in your sewer hose after dumping. It may be visible if you have a clear elbow or connector on your sewer hose. Yeah, it really does help to see and monitor what is coming out of your RV's holding tanks. As gross as it may be.
Oh, ever feel a grittiness when you pull your tank handles? Yup, this is another sign I look for when working on your RV. Valves leak? Uh huh, the grit tears up your gate valve's rubber seals and can cause them to leak. This struvite is some nasty stuff!
So you know or suspect that you have struvite; what can you do? Let's break this down into two steps, removal and prevention.
Removal. First you need to get rid of the struvite from the inside of the tank and plumbing surfaces. This is where you need a professional cleaning service (hey, we DO that!). We do this with the help of a high pressure jet, water, a bit of time, and elbow grease. The high pressure water and our jetter moving around will break the scale build up (see the attached photo) from the inside walls of your tank as well as the plumbing leading from the tank to the sewer exit. Persistence pays off here.
After jetting we back fill the tank with clear water and dump quickly to remove any lingering fragments from the tank. The water coming out of your tank should be perfectly clear at this point. If not, we may jet the tank further or back fill and flush again. Struvite gone! Note: in some very severe cases a de-scaling solution may need to be used. But that's rare, especially if we catch this early. Hence the need for regular and frequent professional cleanings. Yearly is generally acceptable.
Prevention. Since struvite forms in a alkaline pH environment anything we can do to make the fluids — and the liquids you flush — in your tank more acidic (or at least more neutral (pH around 7) will hinder it's growth and formation on your tank's walls and plumbing. The best, and least expensive is to use lots of water! Flush with 2 extra bowls of water after flushing solid waste and 1 extra bowl for liquids.
You could also change your diet to reduce alkalinity and reduce urea in your urine but honestly, that would make your doctor happy but tends to be a bit of a downer when sitting at the dinner table. But hey, maybe this is the reason you pursue a healthier lifestyle. But I won't judge either way. AND! You should be drinking enough water daily. I know, Nag, nag, nag! Sorry!
Trying to prevent struvite in the tank. Be cautious on tank additives that raise alkalinity and supply the bacteria needed for struvite growth. And remember that bacteria, the good and bad kinds, use water to break down solids in your tank. If you don't add enough water you get sticky sludge settling at the bottom of your tank. Another cleaning issue solved with high pressure water and elbow grease.
Thanks for hanging with me for so long on this topic. To summarize: use lots of WATER! LOL I know, broken record. Water is the best prevention along with regular cleanings. In between cleanings try back filling your tanks with the blank tank spray port found on many RVs. If you don't have one consider buying the Valterra Flush King for an efficient way to back fill and flush both black AND gray tanks. I'll have another post on gray tanks in the near future.
Give us a call, text, or email with any questions regarding this topic or tank care in general. Interested in a Flush King or clear connector? I can tell you where to pick them up.
Now let's get you scheduled for a cleaning as soon as possible. Like they say, prevention is the best medicine.
828-573-4299
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www.kleentankofwesternorthcarolina.com
