Reeflo Cavitation issue

[Feet4Fish]

I do have a valve on the outlet which I can/will adjust. You are correct this is a high pressure pump. I purchased it as I planned on supplying two tanks. First would have about 22 ft head and the other has about 15 ft head.

You have what I would have built. A pump with 1.5 inch inlet/outlet should work fine with 1.5 inch plumbing I would think unless one of the fittings is restrictive. I would do what they say.

Water flows from higher pressure to lower pressure. The outlet plumbing cant make the pump flow more than it was designed to do. If you put a 3 inch pipe on the pump the volume coming out of it wouldn't go up magically.

but
I am guessing now
That is a high pressure pump. The flow through the body may be too much for the inlet/outlet size of the pump body with no restriction on the outlet.

So you could put a valve on the outlet so you can throttle the pump a bit and back up some pressure. That seems like a band aid to me but I think it would work.

I think your pump is to big. Not a bad problem to have.

 

[WVNed]

Which is less than half of it's maximum head.
Like I said I have a general understanding of pumps but I have never tried to do what you are doing.
I built my system with less than 2 feet of head through a wall. I can run cheap pumps fine on it and still flow 3500gph..

 

[Reefer Reboot]

Curiosity questions to help troubleshoot;
When you're getting bubbles, is it to both tanks or just one?
Do you have a gate/ball valve on each line after the tee on the outlet side?
Is it possible to get bubbles to just one tank or the other?
How much head pressure do you have on the inlet port of the pump? (How high is the water level above the inlet port of the pump?)
Any restrictive orifice/tare points along the inlet plumbing?
How much head pressure is on the outlet port of the port?
Any restrictive orifice/tare points along the outlet plumbing?
Any pictures available?

 

[Feet4Fish]

Curiosity questions to help troubleshoot;
When you're getting bubbles, is it to both tanks or just one? Just the big display
Do you have a gate/ball valve on each line after the tee on the outlet side? Valve on common outlet and both return lines. Three points of flow control
Is it possible to get bubbles to just one tank or the other?
How much head pressure do you have on the inlet port of the pump? (How high is the water level above the inlet port of the pump?) water is about a foot higher the bulkhead
Any restrictive orifice/tare points along the inlet plumbing? No. Bulkhead - ball valve - Union - pump inlet
How much head pressure is on the outlet port of the port? Combined on the two runs would be about 40 ft
Any restrictive orifice/tare points along the outlet plumbing? T fitting about three feet above outlet
Any pictures available?

 

[pdxmonkeyboy]

This makes sense to me. The reduced inlet is creating a negative pressure which will cause air to be drawn out of solution and bubbles to form. Similar to drawn a vaccum on water and having it boil at room temp.

I have a hammerhead with a big manifold but dont get any bubbles. The longer inlet line is a solid idea but I dont know if it is absolutely neccessary.

 

[Reefer Reboot]

Just from the pictures alone, I see a problem in getting enough feed pressure to the pumps inlet. According to Reeflo, your Tiger Shark has a rated flow of around 8,000 GPH with a downstream head pressure of (I'm assuming by the pictures) about 5 feet. With what looks to be about 12" of incoming head pressure from the sump (again assumption by pictures) going through a 1.5" PVC pipe, you will not be able to get the required flow as you have very low inlet pressure. Please look at this link, https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml
for an idea on the maximum flow rates per PVC sizes at different pressures.
Looking at Reeflo's website, I think this pump is designed more for a multiple story drop down to the pump, thus creating more inlet pressure. There are some things you could do that may help a little like a larger inlet line (although you are ultimately going to be restricted by the pumps inlet size) and having rounded edges on the bulkheads inlet side, but it will be of minimal help. Or just throttle down the outlet as you have done.
I hope this helps.

 

[DCR]

Big boy. A Tigershark

Wow, that's a lot of flow. I can easily see how it would overload your 1-1/2" suction line. I would guess you may be flowing 6000-7000 gph. For that pump to work at that flow rate, you would need a lot more liquid height in the sump than you currently have (like several feet). I doubt that upgrading 15" of suction piping is going to help that much. The entrance loss into the pipe and the reducer are probably too much by themselves. You can try it if you like. It might be enough to stop the cavitation I would throttle back the 1-1/2" flow to stop the cavitation, or you can use a separate pump for the 1" if you wish.

I deal with industrial centrifugal pumps and hydraulic systems for a living as a chemical engineer. It does not necessarily follow that the suction line or the discharge line should be the same as the pump. Doing so will almost always give you excessive pressure losses. You likely have something around 20 ft/sec in you suction line which is extremely high. I would normally size a line like that for 3-5 ft/sec.

The pump you have is really not ideal for your application. It is really better suited for higher head requirements, but you can make it work by throttling it back on its curve. You generally want to run a pump around 30-80% of its curve. It is never a good idea to run all the way back, or all the way out to the end of its curve or you are likely to get into problems like this. Just because a vendor shows it on the curve, does not mean you want to operate there.

 

[Feet4Fish]

Wow! I really appreciate everyone’s expertise. I wish the person to whom I described my pump needs to at MD ( basement sump, 40 Hd ft and two tanks) would have understood everything as well! Reeflo today recommended changing inflow to 2” which I will do and I can raise the water height in the return chamber a bit. I will also valve back the outflow and hope for the best.

 

[pdxmonkeyboy]

FYI, if it comes to it, I was told directly by reeflo that you can throttle the pumps flow down with valves without any negitve affects to the pump.