What is that Hose?

[spartonboat1]

I see permanent oil change units with the manifold systems. I observe a hose that bypasses the pump for some reason. Maybe this is a super easy answer, but what is the bypass hose purpose and/or what is its function? See the red bypass on the front of the oil pump on eBay, linked below:
http://cgi.ebay.com/ebaymotors/ws/e...753412&viewitem=&sspagename=ADME:B:SS:US:1123

Only thing I can think of is that an external pumped fluid can be pushed past the pump, without operating the pump.

 

[Canuck Dennis]

Looks like they put the valves in the wrong place..lol...I do not think that is a factory assembly..

 

[SKYCHENEY]

I had that same question when I helped a friend change the oil on his boat. He had two of those Groco pumps and both had that bypass hose. I tried clamping it off to see if it would pump faster but I could see no difference.

 

[doc g]

Is it a priming hose , shut the valve off and prime the pump by diverting the output to the input???......................Pat

 

[yachtsmanbill]

C'mon... that was a field assembled unit; the guy didnt have 90s but had Ts... didnt have plugs for the 90s but had hose barbs... there is no point to the red hose! ws

 

[MikeP]

The red hose allows some of the output to pump in a loop, thereby lowering the actual GPM and pressure rating. Maybe this was intentional for some reason but I can't think of why it would be helpful.

 

[REBrueckner]

That thar red hose doohickey thingy looks real purty.....let's all put one of them durn things on our raw water pumps!!!!

 

[SKYCHENEY]

I'm telling you that this must be the recommended setup. I've seen it on two other Groco pumps but I still have no idea why they would do this. I told the owner that he should remove those loops, but he felt like it wasn't necessary since it worked fine as is.

 

[MikeP]

Well, perhaps it is specifically designed to reduce the pressure, either on the output or on the gears themselves. It is possible for cold oil to cause the gears to strip - I had that happen on a gear pump a few years ago. Having a bypass (red hose) would prevent that from happening.

 

[Walter P]

Bingo, Mike gets the star for this one. It is a bypass. without it if the discharge hose would be shut off for whatever reason, it would provide sufficient pressure relief to prevent damage to the unit. Serves the same basic purpose as a pressure relief/adjustment valve which diverts the material back to the source.

Walt

 

[Trojan]

Mike and Walt are some what correct, but there must be some type of restriction or check inside the red hose loop. Its not a high pressure or a high output pump. It has a rubber impeller. If the resistance in the output down stream is great enough there will be zero output. As shown, the pump will not create any vacuum. To work there must be a check somewhere in that red hose loop and it's not showing. Or it was just left out. You can over run the pump and it will pump as long as there is not much back pressure. But as for vacuum, as is, it will never draw any vacuum.

BILL

 

[BUSTER]

Walter P was exactly correct.It is a Groco GEAR pump.It has no rubber impeller,but instead has gears and without the bypass and the inappropriate valves were closed it would cause damage.Even though this is a low pressure application this pump is capable of making quite high pressure very quickly
.BTW/It is a very good oil change sysrem.