Hitachi water pump slow to pressure up.

[Daffy D]

Recently my 15 year old Hitachi WM-P 300 finally gave up so replaced it with a new Hitachi WM-P 200xx.

 

The pump works Ok except it takes several seconds to put out full pressure when turning on a tap.

 

What happens is that when turning on a tap there is a low pressure flow of water and the suddenly seems like the pump kicks in and we get the full pressure.

 

This never used to happen with the old pump where we had full steady pressure right from the moment the tap was turned on.

 

I've had a go at Googling but haven't found an answer to cover this particular problem. Lots of "Adjusting the pressure switch" but am reluctant to do that as the pump is only a few weeks old.

 

Could be the pressure tank, perhaps? 

 

Any ideas or preferably a solution would be most welcome.    

 

[Raindancer]

44 minutes ago, Daffy D said:

Recently my 15 year old Hitachi WM-P 300 finally gave up so replaced it with a new Hitachi WM-P 200xx.

 

The pump works Ok except it takes several seconds to put out full pressure when turning on a tap.

 

What happens is that when turning on a tap there is a low pressure flow of water and the suddenly seems like the pump kicks in and we get the full pressure.

 

This never used to happen with the old pump where we had full steady pressure right from the moment the tap was turned on.

 

I've had a go at Googling but haven't found an answer to cover this particular problem. Lots of "Adjusting the pressure switch" but am reluctant to do that as the pump is only a few weeks old.

 

Could be the pressure tank, perhaps? 

 

Any ideas or preferably a solution would be most welcome.    

 

There is a small pressure switch under a grey elongated round grey cover.  If you remove that, on  top of the switch is a small screw.  If you turn it a quarter of a turn to the right, the pump will kick in quicker.  This actually closes the contact to operate the pump sooner than you have currently.

 

However, don't turn too far, otherwise the pump will make a banging noise when water is turned off.  I suggest you remove the electric plug before attempting this.

 

Then carry out the above. And plug back in and try again.

 

It is trial and error as to how far you turn it to your desired effect, without the " thump" every time the water is turned off.   I have left mine alone, as I can accept the slight delay until full pressure is obtained.

 

One other thing to check, is that the pump is fully primed.  There is a grey plastic cap with a cross cut out on top.   Open it slowly by using the stem of a round screwdriver that fits the cross put and slowly turn anti clock wise.  As soon as water starts to seep out, turn it back tightly until water flow stops.

 

Or, if you are not confident to play around with it, call out hitachi under warranty.

 

Hope that helps.

Edited July 16, 2023 by Raindancer
Additional information.

[Daffy D]

4 hours ago, Raindancer said:

There is a small pressure switch under a grey elongated round grey cover.  If you remove that, on  top of the switch is a small screw.  If you turn it a quarter of a turn to the right, the pump will kick in quicker.  This actually closes the contact to operate the pump sooner than you have currently.

 

However, don't turn too far, otherwise the pump will make a banging noise when water is turned off.  I suggest you remove the electric plug before attempting this.

 

Then carry out the above. And plug back in and try again.

 

It is trial and error as to how far you turn it to your desired effect, without the " thump" every time the water is turned off.   I have left mine alone, as I can accept the slight delay until full pressure is obtained.

 

One other thing to check, is that the pump is fully primed.  There is a grey plastic cap with a cross cut out on top.   Open it slowly by using the stem of a round screwdriver that fits the cross put and slowly turn anti clock wise.  As soon as water starts to seep out, turn it back tightly until water flow stops.

 

Or, if you are not confident to play around with it, call out hitachi under warranty.

 

Hope that helps.

Cheers Raindancer, sounds like some useful things to try 

 

Will have a go at it tomorrow 

 

Cheers  

[Raindancer]

You're welcome.  If you need any help, just PM me. 

 

By the way, don't forget to disconnect the power when trying both suggestions of water pump and pressure switch.

Then reconnect and see if there is a difference.   Once the water pump is primed, the only next step is the pressure switch adjustment.

Good luck

21 minutes ago, Daffy D said:

Cheers Raindancer, sounds like some useful things to try 

 

Will have a go at it tomorrow 

 

Cheers  

 

Edited July 16, 2023 by Raindancer
Additional safety advice.

[RanongCat]

For to  pressure switch to  detect pressure drop when on tap can be  slow if system has filter that need replaced. Or if on pressure switch of new pump install "differential "setting is wide a delay  is to be noticed.  To call person who has knowledge of how such can be made is best advice. New pump of  different brand may have different preset.

[xtrnuno41]

Modification pressure switch may cause malfunction of machine and pump parts damage. The warranty will be terminated instantly if you modify pressure switch

 

https://www.hitachi-homeappliances.com/th-en/products/water-pump/image/IM_WT-P100-300GX2_WT-P350-400GX_WM-P150-350GX2 .pdf

 

it is new, better have some checked it. The first line is in that pdf manual.

You are sure you want to start turning on pressure switch? 

[Daffy D]

Unfortunately that didn't work.  

 

First off I started to unscrew the grey plastic cap, as it seemed the easiest thing to do, and checked it was full of water.

Bit unnecessary as the tank from which the pump feeds is higher than the pump so that shouldn't be a problem, but checked anyway.

 

Next had a look under the grey elongated cover. (Check Valve) but there was no sort of adjusting screw, just a round check valve.

 

There is a pressure switch in a round cylindrical unit, but according to the manual touching that would bring down upon me the wrath of Zeus, so left that alone. 

 

While I was at it I also took off the Bladder tank and shook out the water.

 

Non of that worked to fix the pressure delay problem, so guess I'll just have to live with it.  

 

No real problem for me but it's a bit like the old fluorescent lights that always flickered  before turning on. You get used to it, but when LED's came along with instant on, who wants to keep the old  fluorescent.

 

Anyways thanks for you help  

[Raindancer]

No problems

 

I have got used to the slight delay.  And as they say, " if it ain't broke, don't fix it" ????