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What is a Pump Tank?

C-Head offers an accessory called a pump tank that is basically a reservoir for urine until it can be pumped out of the toilet to a holding tank or drain field. It is used in situations where the urine must be pumped uphill to its destination. If the situation allowed for a simple gravity feed draining system, then the EUD would suffice. Having to pump urine uphill is common in sailboats under 40 feet and installations in basements or in underground shelters such as prepper bunkers.

Experimental side mounted pump bracket

The pump tank holds approximately a half gallon of urine, which is plenty of volume for a single use. The tank is pumped out after each use and flushed with a small amount of water to remove the urine from the pumping mechanism. This is primarily to control odor and control the build up of scale in the line. The pump tank is not a water conservation appliance but does eliminate the need to empty a jug or internal urine tank. This is a great convenience for many. When the owner purchases a pump tank, he gets an integrated tank that is anchored inside the toilet and allows the solid waste bucket to be removed without removing the pump tank. A pump is not included (see next paragraph.) The tank drains out of the bottom through a line that can exit on the side or back depending on which best suits the customer. The tank will require periodic treatments to clean out scale in the line. I recommend using a product like ZEP Acidic Toilet Bowl Cleaner for this purpose. Follow directions carefully. It does contain a mild solution of muriatic acid and could damage parts on some pumps so you may want to go with just a straight vinegar flush. In my experience, vinegar is less effective so must be used more often. Comments on other alternative methods are welcome. Scale is one of the biggest problems with toilet plumbing with any system.

There are a number of pump systems that appear viable for the pump tank and I encourage owners to experiment and report their successes and failures. Just remember, Keep It Simple. First lets look at the hand pumps. My initial experiments were with a cheap pump from Harbor Freight ($5). The pump did work well, but is of such cheap construction that the longevity was suspect. Mine lasted about two months. One of my customers reports getting 6 months out of one but the previous one he used only lasted two weeks. He is currently experimenting with this pump that seems to hold more promise.

There is a very heavy duty bulb pump on the market that looks like it has a lot of promise for several reasons.

It isn’t particularly aesthetically pleasing and I am concerned that it may start to smell over time if not flushed with water, and urine is allowed to remain inside of it, but I simply don’t know at this time. I do recommend the Sierra brand at this time because of reviews of the other brands. The Sierra is also rated “EPA Low Permeation” which I take to mean will help prevent odor from permeating the rubber. This is the one I am going to be experimenting with next. I plan on making a bracket that holds it in place and hidden. It can be operated by pressing with the fingertips or with a lever. This pump also has a built in check valve.

One other pump I looked at and have actually used on a boat for fresh water is the Baby Whale foot pump.

I never had any issues with the one I used but the comment sections from vendors is full of complaints of it leaking. There may be some way to prevent this that is easy but it needs to be pointed out. Otherwise, it looks like a good solution. It also has built-in check valves.

No matter which type of pump is used, it must have a well functioning check valve so that urine doesn’t flow back into the pump tank. There are very good individual check valves on the market that will work well but most have a crack pressure of 1 pound which many small electric or hand operated pumps cannot overcome. The Harbor Freight pump could crack the valve but I don’t think that most of the aquarium type electric pumps will be able to.

This system has a lot of promise, since it would be nice to be able to store urine in the holding tank of a sailboat. Pumping concentrated urine into the tank should give more storage capacity, even with flushing the line as long as minimal water is used for that purpose. If you don’t feel that you possess the skills to design an effective, maintenance free system to pump the urine out of the tank, then you should contact a marine mechanic and have him design a system and possibly install it. Admittedly, pumping the contents of a toilet uphill is probably the number one no-no in plumbing if it can at all be avoided. But sometimes it is unavoidable.

I will be doing a separate article on electric pumps after doing some experimenting. Unless specified stated, I am not endorsing any particular vendor or product. I invite you to comment, ask questions and post your experiences below in the comments section.

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