Possible airlock in domestic supply

[Leighb]

Hi,
Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

I am guessing I have an airlock, but how best to clear?

The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

The pump is also reasonably accessible.

TIA

 

[RichardS]

If you don't have easy access to one of the water hoses after the pump, the easiest thing to so is probably to use a piece of pipe over a single tap and suck with the pump running until you clear the air lock. The lowest tap will be best but any should do.

If you do have access to any pipe after the pump, then break it there and suck directly.

Richard

 

[Thistle]

It sounds as though your pump isn't self-priming so it's trying to pull air through the system and failing.

I'd suggest trying either pressurising the tank slightly (block any overflow and a couple of strokes from an air pump into the filler) before turning on the pump and opening the taps one by one.

If you can't do that, then lowering the pressure at the tap is another possibility (turn the pump on, open the tap and suck hard.)

Good luck!

 

[VicS]

Hi,
Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

I am guessing I have an airlock, but how best to clear?

The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

The pump is also reasonably accessible.

TIA

If you can bleed the air from a high point try it.

other wise briefly disconnect the hose from the pump suction to ensure a good flow getting to there. Also check the pump suction strainer,

Disconnect hose from pump discharge to bleed any air out of the pump itself ........ this may be all you have to do ... but don't forget to check and clean the suction strainer.

If you dont have a pump suction strainer you may well have stirred up debris in the tank and got it into the pump valves. If that has happened you may well have to strip the pump and clean any muck from the valves.

 

[Leighb]

Some useful suggestions for me to try, many thanks, I will advise how I get on.

 

[Dull Spark]

It may be worth checking whether there is a pressure relief valve on the top of the calorifier. If so, there may be a red knob to rotate to vent air. This is what mine has. It's easier than breaking pipe joints.
Good luck.

 

[Plum]

Hi,
Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

I am guessing I have an airlock, but how best to clear?

The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

The pump is also reasonably accessible.

TIA

I have this problem after a winter drain-down too. I fitted a new jabsco pump 2 years ago and although it works very well, is is not very good at self priming. It is not an airlock causing my problem. Luckily, my hoses have snap connectors onto the pump so I just break the seal at the pump outlet hose with the pump running. As soon as water starts to spurt out, seal up the connection. I have done this successfully after two winters now.

Www.solocoastalsailing.co.uk

 

[vyv_cox]

I have this problem after a winter drain-down too. I fitted a new jabsco pump 2 years ago and although it works very well, is is not very good at self priming. It is not an airlock causing my problem. Luckily, my hoses have snap connectors onto the pump so I just break the seal at the pump outlet hose with the pump running. As soon as water starts to spurt out, seal up the connection. I have done this successfully after two winters now.

Www.solocoastalsailing.co.uk

I agree. You cannot have an airlock downstream of the pump. The problem lies on the suction side - strainer, pump valves or inlet in the tank.

 

[RichardS]

I agree. You cannot have an airlock downstream of the pump. The problem lies on the suction side - strainer, pump valves or inlet in the tank.

As Plum says, it's probably the pump not able to self-prime because of air in the pump and it can't pump air, although it will pump water it finally gets there .... and sucking on the downstream side is a good way to clear the air.

I've always called that an airlock because the trapped air is locking (i.e. stopping) the water flow but it might not be the correct technical term.

Richard

 

[Dull Spark]

The pump may be above the free surface level in the tank. If so, keep the tank topped up and, perhaps, overflowing while the pump primes.

 

[Leighb]

Thanks to all for your suggestions. I managed to get it working using the tank pressurising method suggested by Thistle - thanks- I actually used a dinghy inflation pump on the overflow outlet as it is conveniently situated on the outside the hull.
However having pumped all the tank contents through so that I could refill with clean water it again failed to prime so I had to repeat the process.
The pump obviously needs an overhaul so that is the next job!!
Thanks again for all the help.

 

[Leighb]

Hi, looking for further advice, the pump is a pretty old looking Flojet the model details have rubbed off so identifying it is likely to be difficult/impossible, so I am thinking that maybe replacement might be the best answer.

The boat has a hot and cold supply to the galley and the heads sinks, so is that 4 outlets or two, given that mixer taps are fitted in each place?
Looking at Jabsco pumps they seem to specify the number of outlets such as 1-3 or 5+ and also a pressure rating.

Prices vary from about £70 up to £160 plus depending on spec. What would be the most appropriate?

 

[Heckler]

Hi,
Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

I am guessing I have an airlock, but how best to clear?

The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

The pump is also reasonably accessible.

TIA

I found that even if you drain the system, the plastic bowl filters before the pump have water left in them. This freezes and cracks the plastic, then the pump sucks air! Guess how I know?

 

[duncan99210]

Hi, looking for further advice, the pump is a pretty old looking Flojet the model details have rubbed off so identifying it is likely to be difficult/impossible, so I am thinking that maybe replacement might be the best answer.

The boat has a hot and cold supply to the galley and the heads sinks, so is that 4 outlets or two, given that mixer taps are fitted in each place?
Looking at Jabsco pumps they seem to specify the number of outlets such as 1-3 or 5+ and also a pressure rating.

Prices vary from about £70 up to £160 plus depending on spec. What would be the most appropriate?

I’ve got 4 outlets on the system (galley, two heads and a shower on the stern): very rare that more than one is in use at a time.... I’ve got a 15l per minute pump ‘cos the Admiral likes a good flow for her showers, it a refit item as the original one wasn’t up to her demands. So, look at the flow rate rather than how many outlets it’s specified for: 12l per minute is OK, less is too slow for our liking, 15 is great but you have to exercise caution about how long your showers are.

 

[Leighb]

I’ve got 4 outlets on the system (galley, two heads and a shower on the stern): very rare that more than one is in use at a time.... I’ve got a 15l per minute pump ‘cos the Admiral likes a good flow for her showers, it a refit item as the original one wasn’t up to her demands. So, look at the flow rate rather than how many outlets it’s specified for: 12l per minute is OK, less is too slow for our liking, 15 is great but you have to exercise caution about how long your showers are.

Thanks that is helpful. We don’t shower on board although in theory we could, we both hate them anyway even in marinas/hotels so we don’t need a high rate of flow I guess.

 

[Leighb]

I found that even if you drain the system, the plastic bowl filters before the pump have water left in them. This freezes and cracks the plastic, then the pump sucks air! Guess how I know?

Thanks, was not the cause in my case as there is no filter fitted! I will be fitting one when I - probably - replace the pump.