Rainman Troubleshooting Guide

Although Rainman water makers are highly reliable, there are some issues that can periodically arise. Click on the symptoms below to identify the most likely resolution.

HP hose vibration, excessive pressure fluctuation, or system unable to come up to 55 bar (800 psi)

Possible Cause:

High pressure pump is starved of water and is cavitating.

Resolution:

This is usually a simple issue to resolve. 95% of the time the issue is due to a blockage or flow restriction upstream from the high pressure pump, causing it to cavitate. There are a number of underlying issues to explore. You are looking for items that can restrict flow to the high pressure pump, so you are searching upstream from there. Check the following:

1. Replace the pre-filter if dirty. A dirty filter can block flow, starving the high pressure pump of water supply. Do not just clean it as sometimes it can look clean but is still clogged.
2. Ensure the pressure supply unit is within 2 metres (6 feet) of sea level. The system being too high can make the lift pump work too hard and decrease its effectiveness. This can starve the high pressure pump of water supply.
3. If you recently changed the pre-filter, did you leave any small parts of the plastic wrapping on it, which may now be clogging the flow in the filter housing?
4. Ensure the pre-filter cartridge is only a particle filter, not a combination carbon and particle filter. Some carbon or dual carbon/particle cartridges are labelled with micron ratings and look like particle filters. These can restrict flow and cause cavitation.
5. The seawater end of the intake hose has a check valve. If something gets in there, it can jam and restrict flow. It is easy to disassemble and check, but be careful of small parts. Turn both sides of check valve counter clockwise against each other and it will separate in the middle. Inspect for items that are small enough to get through the strainer and clog the valve.
6. Is the intake hose damaged and sucking air in? This could be from continual rubbing against a part of the boat that wore a small hole in the hose. If so, this hose needs repair or replacement.
7. If you have installed your Rainman system, check all items upstream from the pressure supply unit to see if something is starving the Rainman of free flowing water. We recommend all fittings on the intake side should be a 3/4’ inner diameter. The Rainman system should have exclusive use of the through hull while in operation.
8. Inspect the impeller on the lift pump for wear. Replace if necessary.
9. Sometimes an air bubble or small debris can get stuck in the high pressure pump, causing cavitation. It can often be cleared simply by restarting the system and increasing/decreasing pressure a few times.
10. A small amount of air in the prefilter is fine, but excessive air that won’t go away (>1’ from top) indicates a likely air leak in the system. Check gasket in prefilter housing.
11. If there are no blockages, then it is possible the high pressure pump packings need replacement. This is extremely rarely the case. Experience has proven that most people getting to this step have missed a blockage in one of the above steps.
AC Unit - System is using more power than expected.

Possible Cause:

Run capacitor.

Resolution:

An AC induction motor requires a run capacitor to keep the voltage and current in phase with each other. If the capacitor burns out, they get out of phase with each other and the ‘power factor’ decreases causing decreased efficiency. The motor starts drawing more current from the generator to do the work that is required to operate at the required pressure and flow rates. This has two effects. First, it increases the current draw of the motor above specifications, which may trip a breaker or generator. If it does not trip the breaker, then the motor will heat up due to increased current, eventually burning out the windings, causing motor failure. If you are interested in further technical information on this, try googling for videos ‘ac induction motor run capacitor power factor’ or similar.
If the capacitor has only recently blown out, and the breaker has been tripping, there is a good chance we can simply change run capacitors in the motor. If it has been running for a while with the capacitor blown out, the motor may need to be replaced. There motor is not particularly expensive, but because of the through shaft to hold both pumps, it would need to come from Rainman.
The simplest way to check if the system is running okay is by using a current meter. A 230VAC system should be operating at approximately 6 amps, while the 115VAC system should be about 12 amps. Alternatively, you can inspect the capacitor box and a burned run capacitor will usually be blackened. This means removing the plastic shell to inspect it.

Salt water drip under high pressure pump

Possible Cause:

High pressure pump packings are worn.

Resolution:

Replace high pressure pump packings.

AC Unit - Generator trips when starting

Possible Cause 1:

Inadequate power source.

Resolution 1:

Try running with a stronger power supply to isolate whether the problem is with the Rainman system or power supply.

Possible Cause 2:

GFCI (ground-fault circuit interrupter).

Resolution 2:

Speak to your electrician about replacing or bypassing this. Some GFCI’s do not work well with induction motors.

Possible Cause 3:

Run capacitor.

Resolution 3:

An AC induction motor requires a run capacitor to keep the voltage and current in phase with each other. If the capacitor burns out, they get out of phase with each other and the ‘power factor’ decreases causing decreased efficiency. The motor starts drawing more current from the generator to do the work that is required to operate at the required pressure and flow rates. This has two effects. First, it increases the current draw of the motor above specifications, which may trip a breaker or generator. If it does not trip the breaker, then the motor will heat up due to increased current, eventually burning out the windings, causing motor failure. If you are interested in further technical information on this, try googling for videos ‘ac induction motor run capacitor power factor’ or similar.
If the capacitor has only recently blown out, and the breaker has been tripping, there is a good chance we can simply change run capacitors in the motor. If it has been running for a while with the capacitor blown out, the motor may need to be replaced. There motor is not particularly expensive, but because of the through shaft to hold both pumps, it would need to come from Rainman.
The simplest way to check if the system is running okay is by using a current meter. A 230VAC system should be operating at approximately 6 amps, while the 115VAC system should be about 12 amps. Alternatively, you can inspect the capacitor box and a burned run capacitor will usually be blackened. This means removing the plastic shell to inspect it.

12VDC Unit - Current draw is higher than expected.

Possible Cause 1:

Battery voltage low.

Resolution 1:

Ensure batteries are fully charged.

Possible Cause 2:

Battery lead too long, leading to excessive voltage drop.

Resolution 2:

Move PSU closer to source and shorten battery leads.

Water tastes salty, TDS increasing unexpectedly.

Possible Cause 1:

Worn membranes.

Resolution 1:

The TDS (total dissolved solids) readings will vary throughout the life of your system. In general, the TDS should be increasing slowly over several years. Most people change the membranes once they get to about 700-800 ppm (parts per million) of TDS. Conditions that can cause TDS to vary include source water TDS, source water temperature, operating pressure (typically lower pressure during brackish water operation), or operating flow rates.If you have a two membrane RO unit, you should split the joiner of the product water hoses and test each membrane separately. It is normal for the first membrane to have slightly higher flow rate and slightly lower TDS than the second membrane.

Possible Cause 2:

Cracked RO membrane or spigot.

Resolution 2:

This is an extremely rare failure. If the TDS level is increasing rapidly over a matter of weeks, it may be possible that the membrane spigot is failing. The membrane should be replaced immediately.

Possible Cause 3:

Pressure vessel O-ring failure.

Resolution 3:

It is not normal for an O-ring on the pressure vessel to spontaneously fail. If there are problems, it is typically after changing the membrane.

Portable Unit. Difficult to insert HP hose into PSU fitting.

Possible Cause:

Worn O-ring inside female side of HP quick connect fitting.

Resolution:

Acquire a replacement O-ring. The correct ring is a -110 (3/8’ ID, 3/32’ section). Using a sharp point, e.g.: a large needle or sharp piece of wire, pierce the old O-ring and pull one side of it out of the groove. Now you can hook it out with a small hook, made from a paperclip would be ideal. To put the new O-ring in, push it down with a small flat head screwdriver or similar, until you can push one side into the groove. You should then be able to push the other side down until the whole o ring pops into the groove.

Air bubble inside pressure gauge.

Possible Cause:

This is normal.

Resolution:

No action required. Liquid filled gauges are the highest quality and most durable ones available. The air bubble is part of design and exists to allow the glycerine fluid to expand and contract as the temperature fluctuates. The purpose of the glycerine fluid is to dampen needle movement.

Impeller in lift pump is swollen.

Possible Cause:

It is more than a year old or stored in too strong of pickle solution.

Resolution:

If the system is pickled in a strong solution for an extended period, it will cause the impeller to swell. This impedes the performance of the impeller and it should be replaced.

Oil drips from high pressure pump.

Possible Cause:

Seals in the high pressure pump have failed.

Resolution:

This is usually a result of not changing the travel plug to the breather plug when commissioning the system. When the pump warms up and there is no breather plug, the air inside the pump expands and forces oil out through the seals. The issue may resolve itself by installing the breather plug. If not, the plunger oil seals are worn and need replacing.

Product water flow is unexpectedly high.

Possible Cause 1:

RO membrane has failed.

Resolution 1:

Check salinity of product water. If salinity is high, follow options above for increasing TDS.

Possible Cause 2:

You are in brackish or fresh water.

Resolution 2:

Brackish water is salty water, but lower salinity than seawater. When you go into brackish water, the product water output increases. If you go above the specified output of your system, you should decrease the operating pressure until you are within the spec. See section in manual on brackish water.

Other issue not listed on this page.

Contact your dealer or Rainman at support@rainmandesal.com. Serial numbers, photos, and videos are always helpful.