SHOWER AIR LOCK / NO PRESSURE

[KIMMO]

I have replaced an existing basic 'Mira' mixer shower with a temperature regulated twin tap valve. Possibl related I also fitted a new basin. The shower is fed from the existing 15mm pipes that fed the old shower. Having fitted it I turned on the tap and nothing happened. Neither hot nor cold. However when the hot tap in the basin is turn on then off the shower (hot) starts allbeit with a pitiful flow rate. Cold seems to work sometimes again poor flow. I measured 4 pints a minute! Theres only about a metre or so of head below the cold storage tank so pressures not going to be great but I assume I have an air lock. Can it be solved by using mains presure to blow back into the tank? There are non return valves that would need removing from the shower unit. Any comments would be appreciated. Matt

 

[Softus]

I reckon you have very low pressure and also restrictive pipework.

What's the exact distance between the base of the cold storage cistern and the shower head (the spraying part)?

Also, is this a house or a flat, and where is your hot water cylinder relative to the shower?

 

[KIMMO]

Softus. distance from base of cold tank to shower head is approx 1.5M. The shower is upstairs in a house and the hot water cylider is mounted on the same floor some 4 metres away. Since it is mounted on the floorboards it lies below the shower valve and head. Could this be a problem. I'm getting about 4 pints per minute out of the hot tap in the bathroom. the pipework dissapears into the floor below the shower and there are several elbows visible. Could I take a 22mm pipe from the cold tank across the roof space and drop down into the shower. Assume something similar could be done with the hot although it would be running a couple of metres above the hot storage cylinder. thanks for your comments Matt

 

[Softus]

Softus. distance from base of cold tank to shower head is approx 1.5M. The shower is upstairs in a house and the hot water cylider is mounted on the same floor some 4 metres away. Since it is mounted on the floorboards it lies below the shower valve and head. Could this be a problem.

OK. None of those things are problems in themselves, but is it possible that your shower valve requires a minimum pressure that is outside what your system can provide (without adding a pump)?

I'm getting about 4 pints per minute out of the hot tap in the bathroom. the pipework dissapears into the floor below the shower and there are several elbows visible.

There's potential here for air locks and debris.

Could I take a 22mm pipe from the cold tank across the roof space and drop down into the shower. Assume something similar could be done with the hot although it would be running a couple of metres above the hot storage cylinder.

Yes - this would be excellent. Also, up and over with the hot isn't necessarily a problem, but install a means to vent out the air at the highest point.

However, check the shower valve MI's before you do this, because changing the pipework won't affect the static pressure, and if that's not enough the for the valve then you need either a valve that will work with tank-fed pressures, or you need to add a pump.

 

[KIMMO]

OK thanks. I wondered about raising the cold storage tank a little. I wont acheive much but I guess I could get 50 cm?
The shower valve is rated down to 0.1 bar but I guess that is borderline. http://www.victoriaplumb.com/Scene_Concealed___Thermostatic_Twin_Shower_Valve.html this feeds an 8" fixed apron head.
what is the relationship between head and distance. I thought 0.1 bar = 1M head.
Thanks for your advice.

 

[Softus]

OK thanks. I wondered about raising the cold storage tank a little. I wont acheive much but I guess I could get 50 cm?

Hm. That's only 0.05 var though.

The shower valve is rated down to 0.1 bar but I guess that is borderline.

It would still work with your head if the pipework was unrestrictive.

what is the relationship between head and distance. I thought 0.1 bar = 1M head.

You are correct.

The quickest way forward for you is to run those 22mm pipes, as you've already described.

 

[KIMMO]

Ok will do. Final question where would be the best place then to take off the hot. I assume somewhere along the pipe that runs up out of the top of the HW cylinder and vents into the cold tank ?

 

[Softus]

Again , look in the shower MIs. They should recommend a point where you can turn down from the cylinder outlet pipe, so that air isn't drawn into it.

The best practise is to fit a purpose made flange to the cylinder. Many use Surrey, Warix is better.

My favourite of all is the Essex, but you need the correct size of hole saws to make the installation as easy-peasy as it's intended.