Tips for troubleshooting an RO filter system

4 min readMay 26, 2023

I have RO filters installed under kitchen sink over the past 7 years. I have replaced many filters (stage 1–3 filters every few months, membrane every year or two). Sharing some tips after years of hands-on experience.

The model I have is this one:

APEC Water Systems ROES-50 Essence Series Top Tier 5-Stage Certified Ultra Safe Reverse Osmosis Drinking Water Filter System, 50 GPD

New Unit Installation

I find the manual that comes with the unit very helpful. For those who are visual learners, there are videos on YouTube with step-to-step instructions. So I won’t repeat here.

The only tip I want to share is to turn OFF the water tank when flushing out a new unit (or new filters). i.e. water should not flow through the yellow tube when you are flushing new filters. Reasons below.

It takes about 5–10 minutes to flush a new unit (you can measure the quality of the filtered water with a $10 TDS water meter). If water flows into the tank while the new filters are flushed, it’ll collect water of lower quality in the tank. Those will be diluted with cleaner water over time. But still, why collect them.

Most Common Issue: Constant draining

When tap water runs across the unit, some waste water would be produced and runs into the drainage tube (black in this model).

If you hear constant draining (more than 5 minutes or so), something’s not right. To confirm the noise comes from the draining tube (not the other tubes), you can wrap your hand around the drainage area. If you hear less noise, it means water is constantly running down to the drain.

I searched online (YouTube) for “reverse osmosis always draining” and found some good instructions. Unfortunately they didn’t solve the three unique problems I had below.

  1. black tube was connected in the wrong direction

The black tube is the only tube with flow control. There’s a sticker wrapped on it that says “do not remove”. The sticker should be closer to the filters, not the drainage (where you drilled the hole on). If you installed it in the opposite direction, flow control would not work and the pressure in the unit would cause more water to be pushed out to the black tube.

When a new unit arrives, the black tube is pre-connected on the filter side. If you leave that alone, it’s hard to get this wrong. Our general contractor somehow got it wrong and it took me a lot of time to troubleshoot (he had also connected other tubes to the wrong endpoints, and messed the orders of stage 1 to 3 filters. The filtered water was more polluted than the tap as a result).

2. unit is not operating at the right pressure

Our general contractor also skipped the small tap that allows tap water to flow directly into the unit. And he has probably thrown it away, so I ended up buying another tap from APEC’s Amazon store. Skipping the small tap is wrong because the unit operates at a certain pressure range. Normal tap pressure is too high. And it’s very hard for you to adjust the main knob to the exact pressure range the filter requires. Even if you get the pressure right by manual adjustment, then your kitchen faucet will have too little pressure to wash anything, and your dishwasher will not have sufficient pressure to operate.

The other woe that follows this mistake is, you have probably have built up too much pressure in the water tank. You will need to let out the pressure in the tank (via its “belly button” under the blue knob), then pump it back to the pressure the it needs (the psi range is pasted on the water tank). You can find how to do it on YouTube.

3. red tube has rusty water stuck inside

The red tube connects the small tap to the RO unit (the inlet tube).

There was one time we had a water outage for several days. When water is restored, rust has built up in the pipe and it took a while to flush those out from all the taps.

It’ll be good to turn off the RO filter tap during water outages. And turn it back on AFTER you flush the rust out of the main tap. Unfortunately we didn’t. It was very hard for the filter unit to flush those rust out. So it was constantly draining to get rid of the rusty water.

One way to flush the rust out of the RO filter is to:

  • prepare a tub below the unit to collect splashing water
  • pull the red tube out (expect to see rusty water running down)
  • let it run until it’s running clear water, then push it back

Words of Advice

It’s tedious but not difficult to install the unit. It just takes patience. I would advise against letting a general contractor install it who may be rushing it and skipping many essential steps in the instructions (mine has brought me more work in the end).

Hope these tips help you to save some bucks on water bills, while enjoying healthy and clean water.