Pump sucking air

[Silver-Fox]

Help required from the gods of MoHo Fun.

I’ve just got the van out of storage, filled her up with water and pump water through the system.

It sounds like air is being sucked into the system and the pressure out of the taps is poor.

I found an issue with the hot pipe at the top of the Truma boiler but sorted that with a proper hose clip.

I’m not loosing anything from the overflow pipes under the van.

Any ideas where to look would be much appreciated.

T I A

 

[Kingham]

More likely to be airlocked. Sounds daft, but as a last resort, are you able to suck on an open tap to help prime the system.

Don’t ask how I know that it helps

 

[Silver-Fox]

More likely to be airlocked. Sounds daft, but as a last resort, are you able to suck on an open tap to help prime the system.

Don’t ask how I know that it helps

I’ve tried having a tap half way between hot and cold and put my thumb over the end hopping it would dislodge any air.

What I can’t figure out is a fairly load sound of what seems air being sucked in.
It’s weird.

 

[pappajohn]

I’ve tried having a tap half way between hot and cold and put my thumb over the end hopping it would dislodge any air.

What I can’t figure out is a fairly load sound of what seems air being sucked in.
It’s weird.

No good putting your thumb over the end, the air is simply moving back and forth and needs SUCKING past the PUMP.

The other thing could be a cracked pump filter housing... The clear chamber on the inlet side of the pump. If this is the first outing since winter it could have froze and cracked. It's replacable

 

[WESTY66]

Cracked pipe elsewhere in the van???

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[Silver-Fox]

I’ve since made another discovery.

The air I can hear being sucked in is from what I thought was an overflow pipe under the van.

Should it be sucking air in as I don’t remember it doing that before

 

[Silver-Fox]

No good putting your thumb over the end, the air is simply moving back and forth and needs SUCKING past the PUMP.

The other thing could be a cracked pump filter housing... The clear chamber on the inlet side of the pump. If this is the first outing since winter it could have froze and cracked. It's replacable

I’ve got no leaks around the pump.

Can I back feed via the shower hose with mains pressure?

Used to do this on domestic stuff when I had an air lock

 

[pappajohn]

Auto dump valve open.
Bet the tank is now empty as well.

 

[pappajohn]

I’ve got no leaks around the pump.

Can I back feed via the shower hose with mains pressure?

Used to do this on domestic stuff when I had an air lock

You're only back feeding as far as the pump outlet. In effect it's a one way valve.
Just suck in the shower hose with pump running, it won't kill you.
Check the dump valve and check tank for water first.

 

[Silver-Fox]

You're only back feeding as far as the pump outlet. In effect it's a one way valve.
Just suck in the shower hose with pump running, it won't kill you.
Check the dump valve and check tank for water first.

Tank ok for water

Dump valve is ok, checked that earlier and the boiler valve holding ok as well.

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[tonyidle]

You can clear a domestic hot water airlock because you have mains pressure cold available. The van has equal pressure hot & cold supplied by the same pump. Sucking is an option that usually works. As does clearing the cold feeds first then opening all hot taps & leaving the pump to run. None of which will help if you have a leak on the suction side of the pump of course.

 

[Silver-Fox]

Are the pumps normally fairly loud and sound like the tappers need setting

I do have it exposed as it lives under a hab seat on top of the tank so easy to get to.

 

[Silver-Fox]

You can clear a domestic hot water airlock because you have mains pressure cold available. The van has equal pressure hot & cold supplied by the same pump. Sucking is an option that usually works. As does clearing the cold feeds first then opening all hot taps & leaving the pump to run. None of which will help if you have a leak on the suction side of the pump of course.

Thanks for that.

I can’t find any leaks apart from the one I found earlier on the boiler side.
Sorted that with a proper hose clip.

Should the filter hold water in it as mine has dropped the water back into the tank

Edit it’s dropped some of it back down not all.

 

[pappajohn]

Well, pump inlet connected to tank, pump outlet splits between cold taps and boiler inlet.
Nowhere for air to enter except a loose pipe between tank and pump or cracked pump filter which won't necessarily leak water as its not pressurised but will let air in as its in a vacuum with pump running if cracked.

 

[Silver-Fox]

Well, pump inlet connected to tank, pump outlet splits between cold taps and boiler inlet.
Nowhere for air to enter except a loose pipe between tank and pump or cracked pump filter which won't necessarily leak water as its not pressurised but will let air in as its in a vacuum with pump running if cracked.

I think you may just get the “I’m a clever b******” award tonight.

Looks like my dump valve has a small by pass.
So it’s sucking in air when the pumps working, but bypassing allowing pressurised water to drip from the dump valve.

From what I can see the dump valve allows water through it in its normal state. So flows through from one cold pipe to the other.

In its dump state the water flows from the tank to the pipe going through the floor.

I’ve now got to figure out how I can make a valve up from fittings from a plumbers merchants.

Any ideas?

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[Neckender]

Have you tried operating the dump valve a few times as it might reseat.

John.

 

[pappajohn]

From your explanation it appears the dump valve has got some dirt in it preventing the underfloor outlet sealing so is drawing air from outside and a little water from the tank
You could try opening and closing the valve a few times to see if it flush out and crud.
If that fails its a new dump valve as I believe they are a sealed unit
Of course, you don't NEED one, it's easy enough to fit a manual drain tap, but if the system does freeze it could be expensive.

In reply to your earlier question.... The pumps are rather noisy, tap, tap, tap, tap.... And if yours is actually sat ON the water tank that will be acting like a drum and amplifying it even more.
May be worth moving it onto the floor if possible

 

[Silver-Fox]

Have you tried operating the dump valve a few times as it might reseat.

John.

Tried that John to no avail

 

[Neckender]

Put a clamp temporarily over the dribbling tube.

John.

 

[Silver-Fox]

From your explanation it appears the dump valve has got some dirt in it preventing the underfloor outlet sealing so is drawing air from outside and a little water from the tank
You could try opening and closing the valve a few times to see if it flush out and crud.
If that fails its a new dump valve as I believe they are a sealed unit
Of course, you don't NEED one, it's easy enough to fit a manual drain tap, but if the system does freeze it could be expensive.

In reply to your earlier question.... The pumps are rather noisy, tap, tap, tap, tap.... And if yours is actually sat ON the water tank that will be acting like a drum and amplifying it even more.
May be worth moving it onto the floor if possible

It’s not the auto one causing an issue it’s the manual one for the tank.

Can’t move the pump but it is sat on the tank on rubber mounts.

I’ll see what I can sort out at the merchants tommorow.

Thanks for all the replies

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[Silver-Fox]

Put a clamp temporarily over the dribbling tube.

John.

Clever sod

I didn’t look at the whole picture.
I can stick a bolt in the end and secure with a jubilee clip

 

[Silver-Fox]

Quick update that may help others in the future.

I removed the dump valve, low and behold it comes apart

There was some c*** hold the rubber off the seat preventing good contact.
It had also shaped itself to the seat over time so this wasn’t helping either.

In true funster fashion I cheaped out and just flipped the seal along with cleaning the seat as well. Kerching valve now working as it should

 

[pappajohn]

Can’t move the pump but it is sat on the tank on rubber mounts.

Try putting it on a foam pad such as a gardeners kneeling pad, they're only about 1ft x 8in and can easily be cut.
The rubber feet are too hard and the tank will amplify the pump noise

 

[pappajohn]

Quick update that may help others in the future.

I removed the dump valve, low and behold it comes apart

There was some c*** hold the rubber off the seat preventing good contact.
It had also shaped itself to the seat over time so this wasn’t helping either.

In true funster fashion I cheaped out and just flipped the seal along with cleaning the seat as well. Kerching valve now working as it should

View attachment 303796 View attachment 303797

Jeez, that's industrial compared to modern stuff

 

[Duck Truck]

Industrial is often better than modern stuff
you can get bits for them

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[Silver-Fox]

Jeez, that's industrial compared to modern stuff

Buy a quality MoHo such as a Rapido and that’s what ya get.

Mind you it’s 13 years old and they built um proper back then

Ohh and the pump now sounds like a Rolls Royce purring