Air lock in new shower hot water supply

[Potemkin]

I have a new shower and pump, installed by a building firm. I tried it for the first time, and discovered that the shower gives cold water but no hot. I suspect this is down to an air lock in the hot water pipe leading to the pump/shower. At its highest point, this pipe has a valve, tall with a screw-cap on the top. If I release the cap, no water comes out. I presume this is meant to vent air in the pipe. No idea how to use it properly though.

Any advice?

Many thanks,
Richard

 

[gas4you]

Try setting shower to hot only. Does shower pump kick in? Try venting when shower is on

 

[Potemkin]

Thank you! I tried venting whilst the shower is on. Lots of air coming out the vent. Hot water coming out the shower. Pump on. Lots of gurgling, which tells me air is moving up to the vent. Should I leave the vent open (do you think it has a one-way valve), or will it suck air back into the system. It is an "IMT Jet 3-bar".

 

[Fluffster]

Do you have a surrey flange or similar where the hot tees from the hwc as this will prevent the air locks.
Pete

 

[Potemkin]

I do have a Surrey Flange (or something similar at least) on the top of the HWC.

Interestingly, the air lock has returned today. No HW from the shower, and the pump stops when the thermostat is turned to Hot. I'll go into the loft and wiggle the valve to release trapped air. Could there really be that much air in the pipes?

 

[Softus]

If you have a Surrey flange then the shower might have been connected to the wrong outlet - could you post a picture?

 

[Potemkin]

I am attempting to post the pictures you requested.
The plastic pipe is the one going to the shower. In fact, it goes up into the roof, runs quite high up, reaching an air outlet valve at its highest point, then dips down to the shower pump.

I tried opening each of the speedfit pipe connectors, one at a time, working back from the pump, until I found water. I figured that that told me where the air lock was. I then waggled the pipe to get the air moving up to the air outlet, and hey presto! The hot water works.

HOWEVER, I'm still getting a lot of air coming down through the shower head, and pressure is variable. Could air be coming into the system from the HWC overflow? Unlikely, I know, but I don't know whether the HWC overflow is higher or lower than the highest point in the shower pipe.

 

[gas4you]

Could be pump sucking air in via open vent!

Fit a surrey flange and pipe the pumped hot off of the side outlet shouldn't need the air vent in the shower hot pipe then

 

[Fluffster]

Looks from the pics you posted that the building firm have just teed off from the hwc and not installed a surrey flange, as gas4u says this is what you need.
Get them back in or diy should be easy as they have used push fit joints.
Pete

 

[Softus]

I do have a Surrey Flange (or something similar at least) on the top of the HWC.

The picture shows that you don't.

diy should be easy as they have used push fit joints.

Disassembling, or cutting away, the old pipework is hardly a large part of the job of installing a Surrey flange.

For example, we don't know where the pump is yet...

 

[Potemkin]

I really appreciate the excellent advice - thank you.
In the meantime, I will consider whether to get in the firm or try to fit the surrey myself.

I'll post some pics of the rest of the run, but basically, the plastic pipe goes about 35 feet to the pump (over hill and down dale), which rests just behind the shower.

I fear that I have some more work to do too..
- The waste from the shower drains slowly, so presumably the fall isn't sufficient/waste pipe diameter was incorrect. That I will have to live with, as the shower tray is well and truly stuck in place.
- Also, turning on the hot tap in the other bathroom sometimes causes the shower pump to switch on in this bathroom, despite the pipes meeting only at the HWC as per the picture above. I suspect a surrey might fix this too.
- Unhelpfully, the basin waste pipe emerges from the wall an inch below and an inch to the left of the pipe from the trap, so to connect them I'm going to have to improvise with some kind of flexible waste pipe. The usual connectors are larger than an inch, and so overshoot where they need to go.
- Also, the basin tap has good cold water pressure (tank fed, not mains) but a dribble of hot, so I also have to sort that one. Might be another air-lock, or dirt in the pipe somewhere.

Ho hum, the delights of paying a building firm by the day, rather than for results.

As I said, top site, top advice.

 

[Fluffster]

Holy you know what!
Have they installed all this using a qualified plumber or is the labourer earining a few quid extra?

The pump should be close to your hwc no wonder you are sucking in so much air, 35 feet away is not acceptable check the mi.
With such a long run any other hot water outlet has a risk of activating the flow switch on the pump , a surrey flange will not stop this.

Pete

 

[Potemkin]

...he agreed that the pump was too far from the HWC, also that the piping ran up throught the loft above the HW vent.

His solution: leave the pump where it is, but drill into the bottom of the HWC and fit an essex flange to the existing pipework. I'm not convinced. Won't this still meant that air comes out of the water in the pipes and form locks?

 

[ChrisR]

Sounds like you have an automatic air vent. They have a float inside which rises to bock a hole if there's water inside, but lets air pass. As you would be able to work out, if there's a negative pressure at the pipe conection, they let air IN.

So they aren't really useful on shower supplies, because even with the pump off, gravity will tend to let water run out of the pipes and air get in. Once they're screwed SHUT they're ok, so they can be used for initial venting, like a manual valve.

Your pump needs top go by the cylinder, have its own supplies from the cold cistern above, and a flange on the hw cylinder.

By the way the pipe from the centre top of the hw cylinder should go sideways pretty quickly before rising to the cistern above (vent) otherwise you get a lot of convection and heat losses from it.