How to Repair and Replace Galley Maid Stator and Rotor in Pump

ANY TIME you observe 'spitting' at a faucet in your water system, it is undeniable evidence of a suction air leak upstream of the pump. Loose hoses, cracked hoses, or the dip tube issue noted below can be the cause. This is NOT to be ignored because it will lead to damage to or destruction of your water pump, regardless of design or voltage.

In a positive-pressure setting there is NO OTHER WAY air can enter the system.

Receiving Your Pump

  1. Inspect the box for obvious damage.
  2. Open box, remove pump, inspect for visible damage
    1. Base plate bent, electric terminals bent
    2. Look at exposed portion of shaft at both ends. If bare stainless is seen, pump was heavily dropped on its end, shifting the shaft. Pumps damaged like this will leak. Save box and packing materials then file claim with shipper. Take photos if possible.
  3. If visually OK, install and operate pump. If it fails immediately, notify us, then file a claim with shipper for concealed damage.
Your claim should be enough to cover your extra labor and shipping costs, and our estimate of damage cost.

"GH" Toilet Pumps

In general, these units (small pump on one end, large pump on the other) furnish water to the bowl at 7 GPM and evacuate the waste at 10 GPM. This means the big pump is sucking air part of the time. It also makes that pump highly aggressive when it is pumping liquid.

All this waste and air needs some place to go, so if there is a restriction somewhere downstream of the pump, it will all slow down and compress, giving symptoms of intermittent evacuation and 'bubbling-back'. Restrictions can be hard objects that pass through the pump, accumulation of calcium deposits, or even blockage of holding tank vents.

The above also applies to "HTS" type pumps (big end only) which use valved fresh water for bowl supply.

Distance from bowl to pump, type and number of PVC fittings used, and relative level of pump and bowl also contribute to overall performance.

These pumps are essentially 'positive-displacement', so if the discharge is blocked, it can virtually lock up the pump.


1. Pump does not operate
   (Solenoid clicking?)

Pump failure, bad
solenoid or control switch
Check further
2. No incoming water Lost prime

Dirty check valve

Worn out stator (SL-7)

Blockage at bowl rim
Adobe Acrobat Download Re-prime pump

Replace/clear check valve

Replace Stator

Clear all holes with
coat hanger

3. Bowl doesn't evacuate Worn out stator/rotor (150)

Debris in waste intake

Problem in boat plumbing
Replace stator/rotor

Slide pump out of
hose and inspect for

Check discharge hose and
fitting for restrictions
(See Below)

4. Pump struggling & trips breaker Holding tank vent blocked

Blockage in discharge line
Clear vent fitting

Clean or replace line
See "Pump Isolation Test" below

5. Toilet bowl bubbles Worn out pump

Discharge restrictions

Air Vent in vented loop
Replace stator/rotor

See below

Clean fittings or clogged
Replace hoses


Bowl fills but does not pump out right:

1. Re-prime waste end:

Fill bowl to below rim with bucket or other source

Go to pump location and gently loosen pipe plug ("PRIMING") on waste end of pump

Allow any trapped air to escape then re-tighten.

Return to bathroom and press flush switch.

If bowl does not empty normally in repeated tests, return to pump location

2. Pump Isolation Test:

Remove 1" discharge hose from top of pump

Obtain a short piece of this hose material long enough to reach a bucket or the bilge.

Install the short hose then give a flush command to unit.

If it flushes normally in repeated tests, problem is a blockage or restriction in plumbing somewhere in the boat

If it still does not pump correctly there is a fault in the pump

Next loosen and remove large waste hose from pump. Breaking the pump free from the hose can be difficult. Use thin screwdrivers to start the hose separation and shoot a little WD-40 in the crack. It may be necessary to demount the pump (four 1/4-20 nuts) and pull pump out of the hose, sometimes with a twisting motion to break that last 30%. There is usually lots of slack in smaller hoses and electrical cables.

Look into the big hole for foreign material possibly wrapped around the T-cutter or rotor. It could be disposable cleaning rags, dental floss or any fibrous material.

Occasionally, on older installations, you can find thick calcium deposits inside the pump nose and the large hose from the toilet. These deposits can be shockingly thick, sometimes over 75% of the nominal opening. In such cases the pump nose and incoming hose must be carefully cleaned. Discharge hoses and fittings would also be suspect.

If no foreign material is visible, problem is likely wear or deterioration of rubber stator or less commonly the brass rotor. Stator should fit snugly on the rotor. In this case, see the procedure for rotor/stator/seal replacement. A New Stator or Other Parts may be required, based on inspection of parts on further disassembly.

If you have a chronic problem during boat operations, check on the back of the toilet bowl where water enters for flushing. You should find a clear 3/8" hose leading from the source elbow to the big white PVC bend. The fittings can get blocked over time and must be clear to pass extra priming water to the pump inlet. If you don't see it, you should install one. We sell these assemblies.

Bowl does not fill:

Assure a source of water to the pump inlet. If vessel has been out of the water, air could have gotten into the system, preventing the small pump from working.

First remove the intake hose from the pump and fill it with water, elevating the end as much as possible to release the maximum amount of air, then reconnect and prime as usual, then test.

Another possible problem is a stuck check valve in the source (or even a blocked sea cock). There should be a check valve near the sea cock. The quickest test for it is to suck on the sea water hose. That not only tests the check valve but often breaks it loose if stuck. Also a tap on the valve body with a hammer can help. Sea water is not harmful to your health.

Procedure: Locking Pump For Rotor Removal on 24 and 32 Volt pumps

(Tools: 1/8" Pocket Screwdriver, normal wrenches)

When pump nose is removed and you are ready to unscrew the rotor…

Remove one of two short ¼-20 hex bolts that secure solenoid to pump case

Insert the small screwdriver into the threaded hole to contact the motor armature

Apply moderate pressure to lock armature while unscrewing rotor. This contact is harmless to the motor armature.

Note that on toilet pumps it may not be necessary to lock motor while reinstalling the rotor

Seal Leaking/Failure

Seal failure is very rare. There are 4 causes:
  1. Incorrect original installation or inferior seal quality.
  2. Hair or certain fibrous material wrapped around the seal, forcing the two sections apart.
    (Can be cured by partial disassembly and cleaning.)
  3. 'Pocket corrosion' or severe pitting of the stainless shaft over long service.
  4. Spring failure due to poor quality or long service with corrosive chemicals added to the flush process.

Seal Kit Installation


To remove entire seal, you must remove "Nose cone" (this is where the stator and rotor are) and remove actual pump housing from motor itself. Once removed flip housing upside down and using screwdriver punch out old seal. Flip over and clean brass area before installing new seal as shown below.

With pump assembly removed, install (black and white ceramic seal in pump housing) make sure rubber side (Black side) is installed towards the pump housing; the white ceramic portion will be facing outwards or towards the Rotor assembly. (Use small amount of lube only on the rubber portion to install) this step only installs White seal with outside rubber sleeve. Picture shows both seals on shaft- The Chrome and carbon seal are NOT to be installed yet! (Pictures are for illustration only and not step by step.)

Seal Assembly

With White Ceramic seal installed in pump body housing, you now can bolt housing back to motor.

Next install (the black carbon seal with SS housing) Shaft seal. With black carbon surface towards white ceramic seal! Use small amount of lubricant, Dish soap or similar on shaft. Not on the Carbon or Ceramic surfaces (this makes it easier to slide on shaft and minimize damage to seal.) DO NOT USE MOTOR OIL OR GREASE. Once lubed Firmly push shaft seal down armature shaft towards housing seal. ALL the way down until it comes in contact with white seal. Twist and push to make sure it is sealed. Install spring (open end) towards seal and end with washer towards rotor, now you can reinstall rotor stator, nose cone, etc.

Seal Assembly Step 2



New style you need to stretch spring. Old Style you do not need to do anything.

The image below shows the difference in the spring of the seal for new style housings vs old style housings. The new style housing (left) is slightly deeper than the old style (right). The spring needs to be stretched in order to fit properly on the new style housing.

Seal Assembly Spring Housing




What is the function of a Vented Loop?
A Vented Loop is an anti-siphon device. It is placed in the line above the water line and allows air in as the waste or water flows through the line. It is to prevent siphoning if your thru-hull or Seacock fails and your toilet or holding tank is below the water line.

When is a Vented Loop necessary?
There are many factors that determine when a Vented Loop is necessary. These are just a few reasons you may need one. Please consult an installer before deciding if you do or do not need a Vented Loop.

When your toilet is below the water line and you're using raw water (meaning the supply water is being pulled to the toilet from the outside of the boat. E.g. lake water / sea water).

You would also use a Vented Loop if your holding tank is below the water line and you do not have check valve that would prevent backflow that could result in siphoning.
Where do I install a Vented Loop if my toilet or holding tank is below the water line?
If your toilet is below water line you would install the Vented Loop in the line between the toilet pump discharge port on pump and holding tank or O/B MSD System-thru hull.

How high does my Vented Loop need to be above the water line?
You should not exceed more than 6-feet of lift in the line to the top of the Vented Loop. It is suggested to have the Vented Loop at least 18-inches above the highest water line.

Vented Loops


Symptom: failure to build pressure (motor OK)

First remove the intake hose from the pump and fill it with water, elevating the end as much as possible to release the maximum amount of air, then reconnect and prime as usual, then test.

Always start the pump the first time against zero pressure.

If pump still won't build pressure, remove nose housing and inspect. Break rubber stator loose. It should be a snug fit over the brass rotor and free of internal roughness or damage from dry running.

In event of dry running damage remove old stator and clean out debris. Brass rotor will clean up with a wire brush and lacquer thinner. Reassemble with a bit of silicone grease rubbed into stator interior and rotor surface.

Center MR-7 Stator flange among the 4 bolts. Then reinstall the nose, tightening the bolts uniformly to "screwdriver" tightness.

If MR-10, assure that stator flange is pressed in the groove in the pump base, then reinstall the nose housing with the 6 machine screws, uniformly. Go around the housing serveral times.

Water Pressure Accumulator Problems

Symptom: short-cycling of pump

Assure that pre-charge pressure is correct

  1. Turn off power to pump.
  2. Release pressure from water system by opening a tap or hose bib.
  3. Locate 'Schrader' valve fitting on the opposite end of the tank from pipe fittings.
  4. Remove cap and measure pressure with standard tire gauge.
  5. Pressure should be about 15 PSI.
  6. If too low, add air with hand pump or compressed air source.
  7. Turn pump power on and run water to test performance.
If problem recurs in days or weeks, the diaphragm inside the tank is ruptured. In this situation the tank must be replaced. We sell these Accumulator Tanks.

Special Problems on old Hatteras Yachts

Air ingestion and resulting stator/pump damage due to chronic dry running.

Hatteras typically used a 'dip tube' to draw water (or fuel) from the tank. They never had a tank drain at the bottom.

They usually used a brass tube for this, but after many years, corrosion from moisture or introduction of bleach into the tank will attack and perforate the dip tube. This allows air to be drawn into the pump destroying the stator, and after many hours, the motor.

In this situation, the dip tube must be withdrawn from the tank and repaired or replaced.

If none of the above helps, CALL US!!!