Air in pumped shower system

[phantom_cyclist]

I have installed a pumped shower system. I used a seperate feed direct from the cold water to the pump and a separate feed from the hot water tank to the pump. The connection to the hot water tank was using a techflange that has a pipe that slopes upwards into the middle of the hot water tank. It then goes down into a u-bend and then an n-bend (inverted U!) to get to the pump inlet. The pump is slightly below the level of the flange output from the tank but the inlet is above this (but still well below the top of the hotwater tank). I have an air bleed valve in the n-bend.

All this is below the level of the coldwater tank.

The water is then piped from the pump, up into the roof space and then down to the shower.

The problem is that every time the shower is run air accumulates in the n-bend and has to be bled out. Also when the shower is turned on it takes several tens of seconds for the water to start flowing (the pump has pressure switches and the pump does not switch on for this period of time).

Any ideas how I stop air getting into the Hot side of the system? Why does it take so long for the shower to start when switched on?

 

[Bahco]

Is the cold taken from the tank also?
This can only be a piping issue, or maybe your tank cannot cope with the volume of water being demanded. Try running your shower and watch if the tank is replenishing itself adequately.

You have a bleed valve on your loop, but is it at the highest point.

Check your pipework again looking for any high spots where air can be trapped

 

[phantom_cyclist]

The bleed valve is at the highest point in the hot water feed, between the hotwater cylinder and the pump inlet.

The cold water is taken directly from the cold water feed and is a seperate feed from that which goes to the hotwater tank.

 

[Panjandrum]

Just for clarification.

Also when the shower is turned on it takes several tens of seconds for the water to start flowing (the pump has pressure switches and the pump does not switch on for this period of time).

You really mean no water at all for that time, then the pump comes on and water comes out? Or does water come out at normal pressure until the pump comes on.
What happens if there is no power to the pump? Does the water still get to the shower - but only at normal pressure?

 

[ChrisR]

Not AUtomatic bleed valve is it - they let air IN.
How hot is your HW? >60 = trubble with cavitation/air separation.

 

[phantom_cyclist]

The bleed valve is manual. I have to unscrew the cap slightly each time until the water comes out of it.

I do not know the temperature of the hot water but surely if any bubbles from cavitation would be downstream of the pump carried along with the water?

I mean that there is NO water to the shower until the pump turns on (there may be something fundamental that I have done wrong but I can't see what!). When I first plumbed it in I put the shower hose on the floor of the tray and waited for the water to come through. In the end I had to suck hard on the hose to get the cold water to flow out of the shower hose. Once through it was OK but at low pressure until I switched the pump on. I niiavally assumed that once the pipes were full there would be no problem from then on due to siphon effect and the fact that the cold water tank must be pressurisinng both the hot and cold supplies to some extent.

I have just tried the shower now with the pump off and the water comes through after a while but it seems to be only the hot water as if I turn the temperature mixer to the hot end I get some water but if I turn it to the cold end I get nothing.

Patrick

 

[Panjandrum]

This is really way beyond my understanding - but if it (the delay in getting water) was my problem I'd be looking for some kind of quirk with the cold feed - but I wouldn't know where to look. And I wonder why you have these n and u bends twixt tank and pump? My power shower has a simple, unbent, connection to the hot supply. Someone is about to tell me now that this is illegal, immoral, or insane.

 

[kevplumb]

simple and easy i would say

 

[Panjandrum]

Aw c'mon Kev - give us a clue. I'm in the mood for weird puzzles tonight but this is teasing me beyond sanity.

 

[ChrisR]

check for dirt in filters. Then take the non return valves out just to try it. from mixer i mean

 

[kevplumb]

if it is air that would explain why the flow switches aint kicking in

 

[jtaunton]

I had kind of the reverse problem, but it might offer a pointer. One of my pump input filters had disintegrated, and the metal from it had worked its way up to the 'ball' in the pump's reed switch.

My shower turned on normally, but when I turned it off, the ball didn't fall back into position, which meant that the pump kept on running for a few seconds until (I guess) the backpressure pushed the ball back down again.

Much turning over and banging managed to get the stray bits of metal out eventually, and maybe you have something similar preventing your start-up ?

(Incidentally, I refer to a ball in the reed switch - This is just based on my best guess at how it works, but I think there is some sort of ball bearing that is captured within the water flow. When the shower is turned on then this ball is pushed up and turns on a reed switch. Apologies if I've got this wrong...)