Mitsubishi pump tank

[BenStark]

I have a Mitsubishi wp305 pump with the tank rusting, so i ordered a stainless one from shopee.

 

Seller send me the 355 - 405 version, which is bigger and more expensive.

 

Of course i can send it back for a refund, and get the right one, but I was wondering if the bigger size is the only difference, and I actually could mount the motor of the wp305 version on it.

 

To me it looks as if the mounts are the same, but maybe the bigger size has a negative effect???

 

[sezze]

If the connectors are the same , and the pressure is the same , it will be ok . I would say even more , it is better . These tanks are for you to have a more constant pressure and also for the pump not switching constant on/off because slightest pressure difference. The bigger the tank , the more the pressure is "regulated" in your system .

In case the pressure of the bladder in the tank is different , then it might be a problem , but not a very big one. It won't operate 100% as it is supposed to do with the normal pressure from the pump diagram. Since these tanks and housepumps are quite similar in end pressure (large difference in flow) i would expect no issues.

Connectors being different , no issue , unless you cannot find the correct connectors to put the pump and bladder tank together.

In short , a bigger tank is better...

[BenStark]

15 minutes ago, sezze said:

If the connectors are the same , and the pressure is the same , it will be ok .

 

Well that is just the point of my post, as I don't know that.

 

In the picture they both look the same, even the height looks same, although a WP305 is lower than a WP355.

 

But since I bought on Shopee, I have only 3 days to send back, and obviously can not attempt mounting the motor, as that will make scratches.

 

So my hope was that someone had tried it before,

 

Thanks anyway for the useful info.

 

BTW, i have replaced a WP355 about a year ago, and couldn't detect a bladder in either the new or old tank.

 

Is the bladder supposed to be easily visible?

[Fruit Trader]

1 hour ago, sezze said:

In case the pressure of the bladder in the tank is different , then it might be a problem , but not a very big one.

 

There is no bladder, pressure is stored in a maintained compressible air pocket directly in contact with the water.

If all of the fittings align correctly there should be no problem using a larger tank.

[BenStark]

6 minutes ago, Fruit Trader said:

If all of the fittings align correctly there should be no problem using a larger tank.

 

That's what I try to find out. When eyeballing both pumps next to each other it all looks the same, apart from the height, but just a 1 centimeter difference is too much of course.

 

That said, why would Mitsubishi not make one tank fits all? It certainly would save them money

[Morch]

I think there's no problem, if the fittings are exactly the same. I'd be weary if there is a marked difference, though.

But to make sure, just contact Mitsubishi and ask them. We went with another brand, but I recall their call center/tech service being quite informative.

Reason for different models is that different countries use different products/specs/systems.

[BenStark]

5 minutes ago, Morch said:

I think there's no problem, if the fittings are exactly the same. I'd be weary if there is a marked difference, though.

But to make sure, just contact Mitsubishi and ask them. We went with another brand, but I recall their call center/tech service being quite informative.

Reason for different models is that different countries use different products/specs/systems.

 

You happen to have a number of the call center?

[Morch]

2 minutes ago, BenStark said:

 

You happen to have a number of the call center?

 

That's Mrs. Morch's domain, and I'm not drunk enough to try and wake her up and ask...

[Fruit Trader]

15 minutes ago, BenStark said:

 

That's what I try to find out. When eyeballing both pumps next to each other it all looks the same, apart from the height, but just a 1 centimeter difference is too much of course.

 

That said, why would Mitsubishi not make one tank fits all? It certainly would save them money

 

The air pocket is maintained by an injector which will likely have increased capacity on pumps with a larger volume tank. Because you are keeping the same size pump and injector I can't see any problem with you using a larger capacity tank.  Most important when fitting these replacement tanks is a good seal on all upper connections of the tank because this is where the air pocket is maintained.

 

It makes sense that pumps with larger capacity require increased pressure storage volume.  

[proton]

These never seem to have the screw holes to attach the top cover like the originals. Strange why Mitsu do not use stainless steel, they always get rust holes after a few years. We got one of these tanks, pump has never worked as well since.

[BenStark]

10 minutes ago, proton said:

We got one of these tanks, pump has never worked as well since.

 

I replaced one over a year ago, and no issues at all

[Banana7]

I got a stainless steel tank from Lazada for my mitsu. Fit perfectly and has been running for about 4 years since the replacement. When replacing, make sure all the fittings are snug and tight. The air pressure regulator seal needs to be sealed perfectly. If all the studs and holes line-up, I recommend keeping the bigger tank.

[NanLaew]

2 hours ago, proton said:

These never seem to have the screw holes to attach the top cover like the originals. Strange why Mitsu do not use stainless steel, they always get rust holes after a few years. We got one of these tanks, pump has never worked as well since.

 

My first Mitsu pump got the pinhole leak after maybe 12 years use so maybe what's in the water makes a difference? I replaced the pump for efficiency then bought a replacement tank, like-for-like, on lazada and rebuilt the old pump as a spare.

[The Old Bull]

Quite often when you order a replacement part you get an upgraded version, this is most probably what you received and should work fine.

[BenStark]

14 minutes ago, The Old Bull said:

Quite often when you order a replacement part you get an upgraded version, this is most probably what you received and should work fine.

 

Nope. the tank for model WP355 - 405 is taller than the one for model WP205 - 255 and 305, and is listed separately and priced differently.

 

I called the Mitsubishi call centre, and they told me the pipe connection is different.

 

So I have returned the tank and ordered the correct one from another seller.

[Ricky HKT]

We had the same problem with Mitsu pumps (tank rusting). 

 

We changed to Hitachi brand, which has a Stainless Steel tank. Also rusting. (Tank, and fasteners / bolts)

 

We eventually changed to Hitachi TM-P turbine pump, as it is mostly plastic/fiber. It rocks! Dependable, high pressure. More money, but seems to be worth it, so far.

[sandyf]

On 1/23/2024 at 10:18 PM, BenStark said:

BTW, i have replaced a WP355 about a year ago, and couldn't detect a bladder in either the new or old tank.

 

Is the bladder supposed to be easily visible?

 

There is no bladder in the tank anymore.  The function has been replaced by a control unit, funny looking item near the pressure switch( Item 16 on the drawing". Had to replace that on a Mitsu pump.

[brianthainess]

At first I had a small cheap pump, it was annoying bcoz using the washing machine and taking a shower was a pain the pressure was not enough. Now with a bigger one no worries all taps can be used no drop in pressure. So yes the bigger the better.

[Fruit Trader]

1 hour ago, sandyf said:

 

There is no bladder in the tank anymore.  The function has been replaced by a control unit, funny looking item near the pressure switch( Item 16 on the drawing". Had to replace that on a Mitsu pump.

 

 

 

Pumps with open pressure vessel have never had bladders. Item 16 on the diagram is the air injector which maintains the pressure storage air pocket in the vessel.

Each time the pump starts a diaphragm in the injector uses pump pressure to inject a shot of air.

[sandyf]

4 hours ago, Fruit Trader said:

 

 

 

Pumps with open pressure vessel have never had bladders. Item 16 on the diagram is the air injector which maintains the pressure storage air pocket in the vessel.

Each time the pump starts a diaphragm in the injector uses pump pressure to inject a shot of air.

Pressure vessels that are "open" are no longer pressure vessels.

On the basis you haven't explained it very well I will take your word for it. In the tech manual the item is referred to as the air control assembly and it was my understanding the bladder did something similar with air in the tank.

I have a multitude of pumps but never come across one with a bladder, but going by the rhetoric on here they must be very common.

[Fruit Trader]

1 hour ago, sandyf said:

Pressure vessels that are "open" are no longer pressure vessels.

On the basis you haven't explained it very well I will take your word for it. In the tech manual the item is referred to as the air control assembly and it was my understanding the bladder did something similar with air in the tank.

I have a multitude of pumps but never come across one with a bladder, but going by the rhetoric on here they must be very common.

 

By open vessel I am referring to there being no isolation (bladder) between the compressible air pocket and the water.

 

The air control assembly as it is called injects air into the tank. The item is made up of several components which is why it is called a control assembly. Control is used in the naming of this device because it keeps the level of air in the pressure tank under control. 

 

The compact house pump range use pre charged pressure vessels with isolation bladder rather than a large tank with air pocket below the pump.

 

 

Example pre charged bladder tank used on compact pumps. 

 

 

 

[sezze]

9 hours ago, Fruit Trader said:

 

By open vessel I am referring to there being no isolation (bladder) between the compressible air pocket and the water.

 

The air control assembly as it is called injects air into the tank. The item is made up of several components which is why it is called a control assembly. Control is used in the naming of this device because it keeps the level of air in the pressure tank under control. 

 

The compact house pump range use pre charged pressure vessels with isolation bladder rather than a large tank with air pocket below the pump.

 

 

Example pre charged bladder tank used on compact pumps. 

 

 

 

That is the type i got also , it lasts about 5 years before the bladder is broken or simply the pressure is gone . Now there is a replacement on which has got a valve so you can pressurize the bladder again ( if it is not broken).

[sandyf]

20 hours ago, Fruit Trader said:

 

By open vessel I am referring to there being no isolation (bladder) between the compressible air pocket and the water.

 

The air control assembly as it is called injects air into the tank. The item is made up of several components which is why it is called a control assembly. Control is used in the naming of this device because it keeps the level of air in the pressure tank under control. 

 

The compact house pump range use pre charged pressure vessels with isolation bladder rather than a large tank with air pocket below the pump.

 

 

Example pre charged bladder tank used on compact pumps. 

 

 

 

Thanks for that, having seen the photo think I may have seen them  in showrooms.

The OP referenced a particular range of pump and was confused by a reference to a bladder. It is a type of pump that I have been fairly familiar with for some years and have only ever seen them with the air control assy but I wouldn't have assumed there had never been one with a bladder hence the way I put the comment.

The type of pump in question is an "on demand" pump and as such controlled by a pressure switch.  I would suggest that no pressure controlled device could be seen to be open so the term "open pressure vessel" that you used is a bit misleading. What would have been more helpful is something along the lines that the type of pump in question did not have a bladder.