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Advice needed on new water pump

Featured Replies

Existing pump appears to have rusted and now leaking. It is a Mitsubishi but not sure of the power

Can someone tell me what are the disadvantages/benefits between constant pressure and automatic with pressure tank pumps (as described on the Home Pro web site) and whether Inverter pumps are worth the extra?

Pump takes water from a tank and feeds a 2 storey medium sized house.

Mitsu pump.jpg

Will probably go for another Mitsu or a Hitachi unless someone has another specific rec but I am not planning to spend for a Grundfoss.

I don't know if it would be an advantage to get an inverter pump, but if that pump has been doing a good job and you are happy with it, I'd just buy the same pump. All the fittings are there already, so you just have to connect the new pump to existing fittings.

If you buy a different pump you will probably have to install different fittings.

If the yellow tank has rusted out you can buy new tanks and install them, but I've never done it.

I have a few Mitsubishi pumps and happy with them.

There should be a tag on the pump that gives it's HP.

Agree with Carlyai.

I also have one of these pumps which is still going strong and trouble free after ten years use.

My pump power is 350 Watts but, unlike yours, it lives in the shade in its own purpose built shed.

Keeping the sun off it is good.

  • Author
2 hours ago, carlyai said:

so you just have to connect the new pump to existing fittings.

If you buy a different pump you will probably have to install different fittings.

Thanks both of you . Normally good points but I am wanting to get some of the pipework changed as still have an underground tank connected which hasn't been used in 10 years (it has a leak in the seal at the bottom and could not find someone to guarantee a fix back then).

Still looking to understand the difference in practice between constant pressure and what I have?

1 hour ago, topt said:

Still looking to understand the difference in practice between constant pressure and what I have?

There is very little difference between constant pressure and what you have.

Your system has a bladder tank utop which sits the pump.

The pump pushes water into this bladder tank until the trapped air pressure increases enough to switch off the pump via a pressure switch.

As the water is used this air pressure decreases until the pressure switch is activated and the pump starts again.

It is the air pressure in the bladder tank which gives you the relatively constant pressure at your faucet.

The pump will automatically try to maintain this pressure by cycling on and off.

If you already know this then ignore what I have written.

  • Author
14 minutes ago, Muhendis said:

There is very little difference between constant pressure and what you have.

Your system has a bladder tank utop which sits the pump.

The pump pushes water into this bladder tank until the trapped air pressure increases enough to switch off the pump via a pressure switch.

As the water is used this air pressure decreases until the pressure switch is activated and the pump starts again.

It is the air pressure in the bladder tank which gives you the relatively constant pressure at your faucet.

The pump will automatically try to maintain this pressure by cycling on and off.

If you already know this then ignore what I have written.

Thanks for responding back. After posting I was looking at the Home pro site and at the bottom of the page after selecting one of the 2 types they had a fairly full description which I had not noticed before. thumbsup

2 hours ago, topt said:

Still looking to understand the difference in practice between constant pressure and what I have?

Unlike traditional house pumps a true constant pressure pump will not cycle on and off around a pressure switch differential but instead keep a constant pressure using a speed controlled pump motor. There are pumps that attempt constant pressure without speed control and do this by monitoring flow and pressure to keep the pump running.

Compact versions of Hitachi and Mitsubishi house pumps attempt constant flow without inverter speed control.

A showers electronic temperature control would be working harder to keep temperature if its supply pressure is rising and falling to the tune of an automatic pump with pressure switch control. Its not a big problem just an example of how constant pressure can be an advantage.

4 hours ago, carlyai said:

If the yellow tank has rusted out you can buy new tanks and install them, but I've never done it.

You can also get stainless steel taks for a few dollars more. All very simple; if you are handy you don't even need to disconnect the motor.

Contrary to popular belief your pump doesn't have a bladder it simply uses air pressure trapped above the level in the tank. To ones with a bladder in a smaller "tank" are controlled by flow not by pressure.

The wattage of your pump depends on the model number.

57b119318cce0_MitsubishiWaterPumpSpecs.thumb.JPG.c3bf1f18f5319d8885d5c7cf7d0c52a0.jpeg

If your pump has been satifying your needs up until now there is no need to change it.

Buy a new tank about 1800Baht, 2500 for stainless one and either change it yourself or call Somchai.

Tanks can be purchased at any small shop displaying pumps- and probably even tanks- that you ride/drive past everyday but never noticed as you didn't need one.

  • Author

Update just in case someone comes across this in the future.

Decided to get a new pump and went for the Mitsu EP-255R2. Saleslady was trying to suggest going for the 300 but I fortunately demurred.....

Not sure of the old wattage (probably 200 but could have been less....) the increase in pressure from what I had is great - except it made an old hose under the sink in the kitchen split.......new kitchen tap required.........☹️

I had replaced one of the old bathroom taps because of some issues including rusting on the tails but hadn't noticed the issue in the kitchen.

I have also now noticed that on an outside hosepipe, when the tap is on but sprayer off, water is forcing its way out around the hose clamp - and the quick connector at the spray end which needs changing.

Just hoping no issues in the glued blue water pipe anywhere........

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