Water Pump Problem

[ftpjtm]

Hello folks,

 

I have a house with 2 underground water tanks connected to a single Hitachi WT100GX2 water pump which is about 6 years old. I typically set the valves so the pump is only drawing from a single tank so if we run out of water we have a full tank in reserve. 

 

Due to the drought and visitors we have been running tanks dry pretty frequently in the past few weeks. In the past few days a problem I haven't seen before has developed. 

 

Everything works fine when running from the tank closest to the pump. But when I switch to the second tank, which is actually the original tank supplied by the builder when the house was new and has worked fine for years, the pump runs continuously. We have good pressure everywhere but eventually the pump overheats and shuts off.

 

Again, when connected to the second tank the pump builds up pressure and shuts off in normal fashion. 

 

And the continuous running is somewhat intermittent, it would not shut off unless unplugged yesterday but so far is working normally today. 

 

It seems like a  minor adjustment of the pressure switch might solve the problem? Anyone have experience doing this?

Edited April 3, 2020 by ftpjtm

[Crossy]

Yeah, it does seem that with the tanks low it's not quite making the cutoff pressure.

 

If you do want to adjust the pressure switch only go 1/4 turn at a time and be aware that (at least in some switches) all the internal metalwork is live!

 

[ftpjtm]

Photos of the pump.

 

Any advice on how to go about adjusting the pressure switch?

 

 

[Crossy]

Most of these switches the cover justs twists off.

 

Turn the adjustment screw 1/4 turn one way. Test.

 

[Denim]

Is it possible to bi pass the pump and just use mains water , saving the water in your tanks for when the mains is off or the pressure is low ?

[ftpjtm]

10 minutes ago, Denim said:

Is it possible to bi pass the pump and just use mains water , saving the water in your tanks for when the mains is off or the pressure is low ?

Yes, but due to the drought we're only getting about 5 hours of municipal water service per 48 hours, so proper operation of the water tanks and pump is more important than ever. 

[VocalNeal]

For some reason the suspect tank level is lower than the original? 

 

Inlet head+pump discharge = outlet pressure

 

As you suspect give the switch a tweak. It doesn't need much. But if you can open a valve to balance the tanks the level will equalize.

[Denim]

9 minutes ago, ftpjtm said:

Yes, but due to the drought we're only getting about 5 hours of municipal water service per 48 hours, so proper operation of the water tanks and pump is more important than ever. 

 

Ah yes , while everyone is focusing on covid19 there is another serious disaster just waiting to happen. Drought. As you say, already happening in some areas but it will spread pretty soon if it doesn't start to rain . Everything is brown where we live and on a recent 5 hour drive across central Thailand saw very few patches of green and a lot of dried up rivers.

[ftpjtm]

I believe I've adjusted the pressure switch to a lower pressure. 

 

But in doing so I notice that the pump motor is leaking water near where I suspect the pump seal would be, which is probably the root problem. 

 

Never noticed this before because I'm typically priming the pump and bleeding air from the system when I have the cover off and its difficult to notice water leaking during all that. 

 

Looks like time for a new pump.