Non-motoring > Lack of hot water. Air lock? Miscellaneous
Thread Author: Bazzabear Replies: 10

 Lack of hot water. Air lock? - Bazzabear
I replaced the cartridge in our power shower today. Because the isolation valves to it are rubbish, I had to turn off the water altogether and drain the hot water cylinder.

I now, despite having the hot water boiler running for over an hour, and the hot water cylinder feeling hot itself, have no hot water.

Is this likely due to an airlock? And if so, what can I do about it?
 Lack of hot water. Air lock? - Bellboy
you probably need to back fill the system with a hose and cold water tap pressure
dont blame me if you get it wrong though
im not a plumber
 Lack of hot water. Air lock? - Zero
yes a way to drive an airlock out is to connect mains pressure water to the hot water tap. You drive the air back up through the system. ONly open the cold tap a nats tho or you blow 5 bar of water into your loft.
 Lack of hot water. Air lock? - Bazzabear
Brilliant. The problem is now fixed, using exactly this method. Unfortunately done before I read the part about pressure caution, but I seem to have got away with it.

And it turns out that my hypothesis about the lack of water altogether from the shower was correct, it too is working perfectly now.

Next question though. In my search for an explanation, I had cause to look more closely at the pump system, a watermill one. It has a separate low voltage water pump and transformer, with the tranformer having a screw adjuster for the pump output - currently set to low.
This suggests to me that I can move it up a notch and get a more powerful shower. Any comments? Worth a try, or likely to blow something up?
 Lack of hot water. Air lock? - Zero
How much head of water to the pump do you have? The death of pumps is a thing called cavitation, it knocks out the bearings. YOu can run a pump faster with more head of water and have no cavitation. The best way is to mount the pump downstairs, it has a large head of water, so you can run it faster and a little hotter with no cavitation.
 Lack of hot water. Air lock? - Bazzabear
The pump is right next to the hot water cylinder, so not much is the answer. Probably best not to take the risk then?
Although it automatically shuts off if there's not enough water throughput for it.
 Lack of hot water. Air lock? - Zero
You have water running if you just select hot but its cold? is that the case?

did you fit the thermo cartridge or a standard one?

 Lack of hot water. Air lock? - Bazzabear
I fitted the thermostatic cartridge. I'm getting no water at all out of the shower currently - I'm working on the hypothesis that there being no hot water supply to the shower is stopping it letting any water through at all.
I have no hot water coming from any tap at all in the house.

I have just tried a trick which I read about elsewhere - trying to force through any airlocks with the cold water mains pressure by covering the end of the kitchen mixer tap, turning on the hot, then the cold, so the cold water supply is forced through the hot water system.
But I sat there with my hand over it for a good minute or two, and the water continued to audibly run through the tap. How long does such a method usually take?
 Lack of hot water. Air lock? - Zero
then it is an airlock. Yes the covering up the mixer tap outlet sometimes work. Did you have the other hot taps open?

 Lack of hot water. Air lock? - Bazzabear
Ah, we've cross posted.

I did not have any other taps open, would that have been better or worse?
 Lack of hot water. Air lock? - Zero
With the hot taps open you can check your idea is working (the water comes out the hot tap) then when that happens you can close the hot taps and fill the rest of the system up.
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