Varying flow on return pump/overflow

[sgdnycct]

HI all,

I've been dealing with this for a couple of months now. I set up my NYOS 440 in October 2025. Everything is doing great but I have this annoying thing going on with my return pump. It's a HYGGER DC3500 (925 GPH I estimate I'm getting half that with height and elbows at 100%). The NYOS came with a ball valve to adjust the drain flow rate. It's a pain but manageable. Here's what's happening:
1. I set everything up, clean pump, reconnect hoses, adjust the drain flow valve so my overflow is about 1" from the emergency overflow intake.
2. Everything works fine for a week or so then one day the volume in the overflow drops (or rises).
3. I readjust everything again. All is well for a few days then suddenly the water level in the tank goes up, pulling extra water from the ATO until it overflows into the emergency drain where is stabilizes. It's not a lot of water so it doesn't cause salinity changes.
4. I adjust again and increase the drain flow by opening the ball valve slightly. All is well for a while then after a few days the water level drops in my overflow so air is getting sucked into the sump.

The only variables I'm adjusting is the ball valve. I've tried cycling the pump to clear out any air that might be trapped. I've checked plumbing to make sure there aren't any blockages (which can't be this because the flow rate seems to go up or down).

Is there anything else I'm missing here? Some basic principle I'm forgetting? The power usage on the pump display is consistent.

Thanks in advance.

 

[TX_REEF]

That's annoying, and happens to me as well with my red sea drain valve. If possible, I would replace the ball valve with a proper gate valve. I have a spears gate valve on my DIY plumbed frag system, and never have this issue (funny how that works, $xxx DIY plumbing > $xxxx red sea plumbing): https://amzn.to/418TmMX

 

[exnisstech]

Maybe try reducing the pump flow when it gets to the e drain instead of opening the valve. Also a little going down the e drain wont hurt and is how I ussually end up running my tanks especially the RS with their diaphragm valve. I got tired of fidling around trying to keep it slightly below the e drain.

 

[sgdnycct]

That's annoying, and happens to me as well with my red sea drain valve. If possible, I would replace the ball valve with a proper gate valve. I have a spears gate valve on my DIY plumbed frag system, and never have this issue (funny how that works, $xxx DIY plumbing > $xxxx red sea plumbing): https://amzn.to/418TmMX

I thought of changing it to a gate valve. I’m trying to avoid that for 2 reasons: 1. I’m not great with plumbing and the NYOS is metric so I’d have to make conversion and adapters in addition to my poor overall plumbing skills and 2. I’m not sure that would solve it? The ball valve makes adjustments a pain but once it’s set I don’t see how the water flow going through it would change. Or am I missing something here?

 

[sgdnycct]

Maybe try reducing the pump flow when it gets to the e drain instead of opening the valve. Also a little going down the e drain wont hurt and is how I ussually end up running my tanks especially the RS with their diaphragm valve. I got tired of fidling around trying to keep it slightly below the e drain.

This is a good idea. I’m going to adjust the pump flow next.

As far as keeping the water at the e level. The problem for me is if the water level is too high in the overflow it becomes much less efficient at skimming the surface. It’s not bad, but I I’d rather keep the skimming going as best as I can.

 

[TX_REEF]

That's annoying, and happens to me as well with my red sea drain valve. If possible, I would replace the ball valve with a proper gate valve. I have a spears gate valve on my DIY plumbed frag system, and never have this issue (funny how that works, $xxx DIY plumbing > $xxxx red sea plumbing): https://amzn.to/418TmMX

I thought of changing it to a gate valve. I’m trying to avoid that for 2 reasons: 1. I’m not great with plumbing and the NYOS is metric so I’d have to make conversion and adapters in addition to my poor overall plumbing skills and 2. I’m not sure that would solve it? The ball valve makes adjustments a pain but once it’s set I don’t see how the water flow going through it would change. Or am I missing something here?

The main benefits to the gate valve are that you can adjust it more precisely, and it is also less prone to partial clogs that cause ball valves to “change” in flow rate without being touched

Totally understand your logical reservations, though. Plumbing conversions are not fun.

 

[mfinn]

I thought of changing it to a gate valve. I’m trying to avoid that for 2 reasons: 1. I’m not great with plumbing and the NYOS is metric so I’d have to make conversion and adapters in addition to my poor overall plumbing skills and 2. I’m not sure that would solve it? The ball valve makes adjustments a pain but once it’s set I don’t see how the water flow going through it would change. Or am I missing something here?

Might want to call Bulk Reef Supply. I know they used to have many different metric conversion fittings. If you were to describe over the phone exactly what you have and what you want, they might be able to set you up and give some reasonable instructions.

 

[sgdnycct]

I thought of changing it to a gate valve. I’m trying to avoid that for 2 reasons: 1. I’m not great with plumbing and the NYOS is metric so I’d have to make conversion and adapters in addition to my poor overall plumbing skills and 2. I’m not sure that would solve it? The ball valve makes adjustments a pain but once it’s set I don’t see how the water flow going through it would change. Or am I missing something here?

Might want to call Bulk Reef Supply. I know they used to have many different metric conversion fittings. If you were to describe over the phone exactly what you have and what you want, they might be able to set you up and give some reasonable instructions.

Thanks for the suggestion. I actually did speak to them. They told me what I needed pretty specifically but don’t carry the parts! With the instructions they provided I was able to find everything online. I’m just hesitant to mess with the OEM plumbing and end up making things worse.

 

[mfinn]

Thanks for the suggestion. I actually did speak to them. They told me what I needed pretty specifically but don’t carry the parts! With the instructions they provided I was able to find everything online. I’m just hesitant to mess with the OEM plumbing and end up making things worse.

A lot of us didn't have any training in doing plumbing, but through a little trial and error figured it out.
Doing mock-ups and just holding up the new run next to the old one can show how easy it is.
Maybe if we keep talking about this someone can be specific and detail their process dealing with your issue.

 

[sgdnycct]

Thanks for the suggestion. I actually did speak to them. They told me what I needed pretty specifically but don’t carry the parts! With the instructions they provided I was able to find everything online. I’m just hesitant to mess with the OEM plumbing and end up making things worse.

A lot of us didn't have any training in doing plumbing, but through a little trial and error figured it out.
Doing mock-ups and just holding up the new run next to the old one can show how easy it is.
Maybe if we keep talking about this someone can be specific and detail their process dealing with your issue.

Thanks for the encouragement! Did my anxiety come through? it does scare me a bit.

 

[mfinn]

Thanks for the encouragement! Did my anxiety come through? it does scare me a bit.

I think the initial anxiety is justified. We are dealing with water in our homes and the potential of putting water where it doesn't belong ( on the floor).
I have to change out a pump on my system ( closed loop) and there will be some plumbing modifications. Some I know about, some may show up. I am putting it off because of that anxiety too, but I know once I start it, things should go as planned.
You make a plan, ( draw it out on paper with measurements ) gather all the necessary parts and tools. Make sure the measurements are correct.
And maybe see if someone in your area you know can lend a hand. Local fish store employee?

 

[sgdnycct]

Thanks for the encouragement! Did my anxiety come through? it does scare me a bit.

I think the initial anxiety is justified. We are dealing with water in our homes and the potential of putting water where it doesn't belong ( on the floor).
I have to change out a pump on my system ( closed loop) and there will be some plumbing modifications. Some I know about, some may show up. I am putting it off because of that anxiety too, but I know once I start it, things should go as planned.
You make a plan, ( draw it out on paper with measurements ) gather all the necessary parts and tools. Make sure the measurements are correct.
And maybe see if someone in your area you know can lend a hand. Local fish store employee?

That’s a great idea.

Question is will this solve it? With my current set up the flow changes up and down so it can’t be the valve getting blocked. Adjusting it isn’t great but it’s not manageable.

So, if it’s not an adjustment issue and we assume it’s not a blockage issue would switching to a gate valve help? I’m suspecting it’s the pump. Could it be that the pump varies the flow for some reason? Maybe an electrical draw issue?

 

[mfinn]

That’s a great idea.

Question is will this solve it? With my current set up the flow changes up and down so it can’t be the valve getting blocked. Adjusting it isn’t great but it’s not manageable.

So, if it’s not an adjustment issue and we assume it’s not a blockage issue would switching to a gate valve help? I’m suspecting it’s the pump. Could it be that the pump varies the flow for some reason? Maybe an electrical draw issue?

Doing the process of elimination is good. Start with the easiest.
Sounds like it could either issue. Pump or the valve. Probably the easiest would be to change the pump.
I have not used that brand of pump before, but any pump made can have issues.
If you did, make sure the connection in the piping will match the new pump.

 

[mfinn]

That’s a great idea.

Question is will this solve it? With my current set up the flow changes up and down so it can’t be the valve getting blocked. Adjusting it isn’t great but it’s not manageable.

So, if it’s not an adjustment issue and we assume it’s not a blockage issue would switching to a gate valve help? I’m suspecting it’s the pump. Could it be that the pump varies the flow for some reason? Maybe an electrical draw issue?

On my 66 gallon lps tank I run a herbie style overflow. Main drain, with an emergency drain. I use a Vectra M2 pump. It's been on it for 6-7 years.
Every once in a while, maybe every couple months I hear water running in the emergency drain aor sucking water from the main drain, meaning my system is out of balance. I will give the gate valve a very tiny adjustment either way and it it usually clears up within seconds. I attribute that to build up of either a little algae or just biofilm or maybe even a little sponge.
The point is, with the gate valve it takes only a very slight tweak to the gate valve and it corrects the situation for me.
Once every few months isn't a big thing IMO.

 

[RoanokeReef]

I have a 300 and bought parts from https://store.coralvue.com/replacement-parts/plumbing?cat=941 when I needed to add some piping. I'm thinking about switching the ball valve out to the new red sea kit. It comes with the fittings needed - https://redseafish.com/kit/reefgate-valve-upgrade-kit/

 

[sgdnycct]

I have a 300 and bought parts from https://store.coralvue.com/replacement-parts/plumbing?cat=941 when I needed to add some piping. I'm thinking about switching the ball valve out to the new red sea kit. It comes with the fittings needed - https://redseafish.com/kit/reefgate-valve-upgrade-kit/

Do you know which kit is the right one for the NYOS? I’m assuming the 300 and 440 are the same pipe sizes.

 

[RoanokeReef]

Do you know which kit is the right one for the NYOS? I’m assuming the 300 and 440 are the same pipe sizes.

I believe they are -

Upgrade kit for REEFERs 32mm / 1” Down pipe​

 

[BryanM]

I thought of changing it to a gate valve. I’m trying to avoid that for 2 reasons: 1. I’m not great with plumbing and the NYOS is metric so I’d have to make conversion and adapters in addition to my poor overall plumbing skills and 2. I’m not sure that would solve it? The ball valve makes adjustments a pain but once it’s set I don’t see how the water flow going through it would change. Or am I missing something here?

To make meaningful change here I think you need to embrace changing the valve type.

I had a redsea with that awful diaphragm valve, and I went through exactly what you're describing.

I since upgraded tanks to a waterbox 230.6 with a proper gate valve, and I rarely have to adjust.

 

[X-37B]

Before you change anything shut off your ato and open the drain valve 100%. I run 4 systems with gate valves, one is a red sea which has the worst valve.
My main system is 2 years old. Every so often water will go over the emergency and drain into the return. This tells me that there is some restriction in the overflow pipes. Could be algae, snails, or just buildup in the lines.
I call this the flush. Run it for several hours then reset it to proper flow. Works well and I run both ac and dc returns.
I have done the same over the years with standard ball valves too.

 

[TX_REEF]

Before you change anything shut off your ato and open the drain valve 100%. I run 4 systems with gate valves, one is a red sea which has the worst valve.
My main system is 2 years old. Every so often water will go over the emergency and drain into the return. This tells me that there is some restriction in the overflow pipes. Could be algae, snails, or just buildup in the lines.
I call this the flush. Run it for several hours then reset it to proper flow. Works well and I run both ac and dc returns.
I have done the same over the years with standard ball valves too.

really good, simple idea. I'm gonna try this myself with my annoying red sea reefer.