Leaking pump tank diaphragm

[passingas]

Has anyone ever had any luck in fixing a leaking pump tank diaphragm? We bought it (Hitachi WT P300 GX) 8 years ago and it's ran flawlessly up until very recently.  It's coming on excessively and now I'm seeing a trickle of water where the upper portion of the tank (actual pump and electrical connections) joins to the rest of the pump tank (diaphragm???). Or....is it one of those things, where one has to buy an entire new pump? I'm pretty much sold on the fact that we can place humans on the moon and get them back, a tank diaphragm repair should be cake. Hmmmmm.....TIT, though.....eh? Has anyone ever tackled this issue, here? pg

[Crossy]

Can you post a photo of where it's leaking from.

 

If it is the diaphragm then the solution is a new tank which on an 8 year old pump may be unobtainium.

 

[passingas]

Thanks Crossy for that quick reply.....

Unobtanium....is that a new metal? 5-5-5 Yup, that's what I'm afraid of...I'd have to find one made of oldanium and not sure if they ever got around to making that stuff. At first glance, I really don't see how I could detach the upper part from the lower part and not sure it would do any good anyway. I've seen schematics of how air bladders work, but not any showing how they attach. Hmmm.....

[Crossy]

That pump is still available https://www.homepro.co.th/product/1063270 so there is a chance you could get a new tank.

 

Taking the beast apart would be the next process, you'll have to strip it to fit a new tank anyway.

 

[passingas]

After realizing that it will still get water up into the house even with it leaking water....I'm now thinking (whoa, what a concept, eh?) it's not the air bladder...it seems to be doing its' job just fine. It's leaking a trickle of water....not air, hence probably not the bladder??? But it is in the part where all of that attaches. Wondering now, if it could just be a leaky tank? I've got some 3M 5200 (that almost magic, marine sealant/adhesive that will cure under water.....), perhaps I'll just apply a thin film of that on the tank (joint), where it's trickling water from. Will probably have to remove the plastic upper base to get to the actual joint. However, even that doesn't lend itself as to how one would go about that. Guess it's time to remove any and everything off the top and go from there. Stay tuned......Hmmm....

[Crossy]

Just now, passingas said:

Guess it's time to remove any and everything off the top and go from there. Stay tuned......Hmmm....

Time for a blow-by-blow picture thread methinks

 

[passingas]

Thank you sir, for that link. I'll repost if/when I can get it fixed. pg

[Crossy]

If you're really lucky it's just a seeping gasket between the main pump and the tank.

[passingas]

As per Crossy's request and his last comment...

It turns out to only have a wield seam on the bottom....that plastic thing is ....not really sure what it's for....6 nuts off and everything comes off (in one piece or at least still all hooked together). The only thing that could possibly leak would be the only gasket going to the tank. It shows no sign of any wear, but cleaned it up anyway. So it must be that gasket as the tank is definitely not the problem...I hope. Close examination reveals water seepage stains coming from the gasket. That white tube is connected to something and wouldn't come out. Here're a few pics. I hope this might help others.

[VocalNeal]

I don't believe there is a diaphragm. Just that the tank is leaking or more likely because it is at the top where no water usually gets to it is one of the gaskets above leaking and dripping down. 

I also believe that if you go to a local shop sealing Hitachi pumps they will sell you a new tank. For a Mitsubishi they will so you simply need the Hitachi dealer. They are about 1600 baht for a Mitsubishi. You may also be lucky and find a local SS replacement I think they are about 3000. 

 

EDIT OK I see you beat me to it. You need a trip to the big city for a new gasket or slap some silicon around it or spray with WD-40 and leave for a while to swell the "rubber". If you do ever get a pin hole it can be fixed like the old tinkers used to do by drilling out the weeping bit and covering a self tapping screw with silicon and a piece of rubber and screwing it in. This is only a stop gap as soon another hole will appear etc, and. and.

[wayned]

I rebuild Mitsubishi pumps all of the time but have never rebuilt a Hitachi.  I would go to an automotive supply store ans but a tube of RTV (form a gasket) and put a good dollop on both sides of the existing gasket before reassembling it.  I use it all of the time.  Here's the email for Hitachi service if you want to contact them regarding replacement parts. E-mail : [email protected]   I have IPLs for Mitsubishi pumps, but not Hitachi.

[passingas]

Well I guess all it needed was a little TLC and a good cleaning....must of got tired being a dirty pig...it's all hooked back up and working like a charm. No drips, no recycling....just humming along when a spigot is opened. By the way....the only gasket you'll encounter on top of the tank (under the pump) needs to fit around that white flange (it raises some for ease of placement, so it seats under it and above it), not just sit on top of said flange like one could surmise by looking at the picture. Thanks again to Crossy for the prodding and suggestions. As someone once said...seek and ye shall find.

[Pib]

Glad the OP got it fixed. 

 

There is no tank diaphragm in these types Hitachi and Mitsubishi pumps....nothing separates the air and water within the tank with the air setting on top of the water.   This means the air would naturally be absorbed into the water over a short time, but these types of pumps have an "air balance/control valve" which feeds a tiny bit of air back into the water tank to keep the air charge at the proper level which keeps the tank from getting waterlogged. 

 

I circled this valve and it's associated tube which goes back to the water input...when the pump turns on suction from the tube pulls open a rubber diaphragm/spring assembly which allows a small amount of air to be sucked in and injected into the tank which keeps the air charge at the proper level....keeps the pump from becoming water logged.  Now when that little rubber diaphragm within the air control valve ruptures (even a pinhole size) water can leak from that valve and the valve stops working which causes the tank to become waterlogged after a few days to a few weeks.  

 

 

 

 

Edited October 14, 2017 by Pib

[passingas]

Thank you PIB for that great bit of info. Now I know....and by the way, that black plastic thing on the tank top is there to secure the housing shield for the motor/pump, etc. And of course, guess who started bolting it all back together, before...putting it back on????  Live and learn, eh? Again thanks to all who inputted on this. pg

[Pib]

For you Mitsubishi pump owners the Air Control Valve assembly is that 6-sided assembly (circled in below image) that screws into the top of the tank vs the 4-sided assembly mounted on the intake manifold on a Hitachi pump. 

 

And just as with the Hitachi air control valve an input tube runs back to the pump's water inlet which applies suction each time the pump turns on which in turn activates the air control valve to inject a tiny amount of air back into the tank to replace absorbed/loss air. 

 

[wayned]

.I emailed the Hitachi service center on the email that I posted in post #11 and they sent me a complete IPL for the WT-P pump.  For some reason I can not copy it here so if you want me to send it to you along with a contact I will forward the email to you.  Just PM me with your email address.

[passingas]

Thank you, but I have that already scanned and saved. I should print it out to have forever....someday....again, many thanks. pg