Fresh water airlock problem??

[Brianmor]

I've just drained down the fresh water on my underchassis mounted water tank to calibrate a new external bluetooth water level sensor. I kept one of the taps open so I could run the pipe nearly dry. I filled the tank up and the pump is running although it's making a slightly different noise from normal but no water from any of the taps. Obviously there's a big airlock, so I took the shower head off and sucked the water through and the water is now gravity feeding on the floor down the drain. The pump/system has obviously still got air in it. I can't get my mouth around either of the sink taps to suck the water out due to their size and position, any suggestions? The pump is 2 months old and it's internally mounted with no access without dropping the whole water tank.

 

[DelViv]

I had a similar issue after picking up my latest MH. If you have mixer taps, you need to open them when they are half way between hot and cold. Make sure ALL taps are open at least a little and then turn on your pump. I got a few gurgles and spurts but after a minute or so it all calmed down. Could be worth a try if you haven't already done this.

 

[Brianmor]

I'll give it a try. I've found an adaptor to fit the sink taps and I've sucked the air out of all the cold lines which are now flowing by gravity. The problem seems to be with the hot water lines which I can't suck water through.

 

[Trikeman]

I'll give it a try. I've found an adaptor to fit the sink taps and I've sucked the air out of all the cold lines which are now flowing by gravity. The problem seems to be with the hot water lines which I can't suck water through.

Brian, your heater drain down tap isn’t open is it?????
Countless times seen (and done) that.
Worth a quick check.
Kindest Regards
Trikeman.

 

[Brianmor]

No, I wish it was. I'm now trying to backfeed water through the shower hose to ensure that the pump is primed. The clown of a designer at autosleepers should be castrated with a blunt knife for putting the water tank under the floor with no access.

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[GeoffnDee]

There should be a non return valve in the system , either fitted on the in-tank pump or inline (it could be near the hot water boiler input) ,but if there is not one fitted ,or you cannot get to the pump , it could be worth fitting an inline non return valve to stop this problem in the future.

 

[Brianmor]

Where would you fit this valve, and if fittes how would you drain it in the winter?

 

[Landy Andy]

Fit the valve anywhere easily accessible after the pump.
To drain down you push/blow the water through the valve so the water comes out the drain valve, frost valve, and taps.

 

[GeoffnDee]

As the non return valve is normally fitted on the top of the pump I would fit it as close to the pump as is possible and easy to get to , If you drain down in the winter using the pump switched on with the tap open this will still work , or , if you have a drain tap in the water pipe system this will still work in draining the pipework (with the taps left open).
If you have a drain tap on the tank this will still work in draining the tank , which will have an air vent, and you could disconnect the pipes from the non return valve for the Winter if you want to confirm total drainage of the water pipes.

 

[tonyidle]

If it's a diaphragm pump (Shurflo type) it doesn't need to be primed and will pump air as well as it does water. Close all taps then let it pump for a while then open cold only. Once water appears at the cold taps open the hot taps. Before doing any of this you have allowed time for the boiler to fill I assume?

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[Brianmor]

Thanks to everybody for their helpful replies. I'm back in business, I totally drained down and then refilled really slowly with all the taps open. Started the pump and 30sec and several gurgles later I'm a happy bunny.
My next job will be to install an external Surflo pump and one way valve.

 

[DelViv]

Glad you got it sorted

 

[GeoffnDee]

I doubt if you will need a non return valve with an external diaphragm type pump , it is the in- tank type of pumps that work and prime much better with a non return valve fitted in the water supply system

 

[pappajohn]

If water Is flowing from all taps by gravity it's not an airlock....
But I can't see how water can flow uphill by gravity, it needs an open end below water level to acheive that..sounds like the impeller in the pump isn't turning fast enough even if the motor is running

 

[Landy Andy]

Can you see the pump?

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[mikebeaches]

We regularly have a similar / same problem as the OP after our tank has been drained down.

I think our pump is by Sureflow, but it isn't firmly mounted, just attached to the end of the pick-up pipe in the freshwater tank on our PVC.

We were in Spain with the problem, when a Funster on here suggested "arm into the top of the tank (which is accessible from inside the van - just), grab hold of the pump whilst it is submersed in plenty of water and bang it against the side of the tank while a tap is turned on".

WORKED! And has done many times since. Bit of a faff because access isn't easy, but appears to be a solution.

Previous van had a fixed pump and we could often clear an airlock by tapping / hammering on the pump, taking care not to break or damage it. Fortunately, airlocks were not so frequent in that van.

 

[Brianmor]

I had an adaptor fitted to the end of each tap with a pipe running below the level of the fresh water

 

[Brianmor]

Can you see the pump?

Pump is totally inaccessible without cutting holes in the floor and tank or dropping the tank

 

[Brianmor]

Just as an aside, the new Mopeko water sensor works really well and gives an accurate display of the water level. Previously you only knew how much water was left was by filling the tank completely and then emptying and counting buckets from the waste tank over the following few days

 

[Bart]

Thanks to everybody for their helpful replies. I'm back in business, I totally drained down and then refilled really slowly with all the taps open. Started the pump and 30sec and several gurgles later I'm a happy bunny.
My next job will be to install an external Surflo pump and one way valve.

We have an autosleeper kingham with an internal pump , what a piece of shit it it , it was working fine then the other day when we are in France topping up the water , came back in tried water...nah pump was whirling like mad but no water. So I started to try to Syphon feed it vai the normal hose / adapter we usually use when this happens ,, nah nothing , in the end I got below the MH and gave the side of the water tank a good thump with my first , boom pump started to work again. When we get back I'll also look into getting an external pump.

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[tonyidle]

Submersible pumps flow as much, if not more, than external ones. They generate more than enough pressure for a motorhome system. They are cheaper to buy, cheap enough to carry a spare, and modern ones have a built in bypass to clear any trapped air. The Reich twin pump (for example) is also available with an attached one way valve.