Vent for Shower Pipework in Loft

[DIY Bob]

A long time since I've been on here, but I need some more advice.

Our 'spare' bedroom has a Mira power shower. The hot water is fed from the HW cylinder which is more or less on the same level but about 5 metres away, and the pipe runs up into the loft, and back down into the shower unit. The cold water is fed straight down from the tank in the loft.

It worked fine for years when my daughter lived here, as she used the shower daily. However, since she moved away, it's not used that often, and the up-and-over hot water pipe gets full of air.

Would it be okay to tee into the pipework in the loft and vent it over the tank, same as the HW cylinder is?

Thanks for any advice.

 

[Best]

Probably not Bob! Will draw air down.
You could try putting a tee on the pipe on its higher level and a manual vent on it.
Auto vent might be better but hope it doesn't allow ingress of air while shower is on.
Hot pipe rising & falling never a good idea. If you run the shower on cold & turn it to full heat, the air in hot pipe might clear, especially if handset is good flow or removed.
An air free supply would help but is never really air free so will probably airlock again

 

[Ch4 plumbing]

How does the shower hot tee in? Maybe a Surrey flange would help.

 

[DIY Bob]

Thanks for the quick replies.

The shower hot feed is fed from a Surrey flange, but here's the thing - the hot feed is teed to feed my main shower as well (I know, I know). The main shower is a bit more conventional - the feed comes down to a shower pump at floor level next to the HW cylinder and then off to the main bathroom. That works fine, but I guess it doesn't really help the situation with the up-and-over power shower!

There's not much point in putting a manual vent in, because I can already clear the air by lowering the shower head to the shower tray and the pump eventually drags hot water through. It's just a nuisance, and the noise scares my daughter if I forget to do it before she visits! And no doubt it doesn't do the power shower pump much good.

An automatic bleed valve sounds interesting - presumably that lets the air out (but not the water!) but doesn't draw air in when the pump is working.

I am not familiar with them - does it just fit on an upright piece of pipe teed onto the shower hot feed in the loft? And is it critical to fit the valve above or below the water level of the cold tank? (I assume that it should be below the water level in order to work, but I'm not sure)

 

[DIY Bob]

Hmm. Just looked at a 'plumbers parts' video on YouTube to get a beter idea. It seems that it's not a good idea to fit an auto bleed valve on the suction side of a pump (as it would be in this case) 'cos it won't seal and will drag air in.

So unless anyone's got a solution, it looks like I will have to carry on with the situation for now.

As I said, it wasn't a problem when the shower was used daily, but now it's only used occasionally the air gets in from somewhere.

 

[Best]

An auto vent would need to be below the level of the water level in the cold water tank for your situation. It will have the danger of sucking air in.
Hot pipes overhead are not a good idea. Hot water when it cools down releases air as far as I know. The best way is to have the hot supply to the shower fitted going downwards.
One way to sort it - but a bit of an over engineering idea, is a open brass vessel type air vent in attic. Flamco actually make a similar thing. Basically an open vessel with the pipe connected to each side of it and an auto vent screwed into the top of it. Pumped water will not draw air inwards

 

[Best]

Flamcovent is its name. Here is a video of it.
https://m.youtube.com/watch?v=zmJtWLpv2ZA

 

[DIY Bob]

Thanks Best.

The Flamco set-up sounds a bit too much for my limited DIY skills.

I did toy with the idea of teeing a pipe from the hot feed to vent over the CW tank, but with a non-return valve in-line to try to stop air being pulled back in when the shower is running (bearing in mind that the system is already vented at the top of the HW cylinder anyway, so I would not be obstructing the main vent). But the 'extra' vent might not have enough head or volume of water beyond the non-return valve to prevent the air being pulled in. Any views?

It might be worth a try - if it doesn't work, I can just cap the tee off.

If there's nothing else I can do, I will have to put up with the hassle until the next time I do up the shower room and run the hot feed under the floor.

 

[DIY Bob]

Thanks Best - I've just seen the video on the link you sent me. My Slovenian is not up to much, so I'll have spend some time on google translate to find out which bit of kit is the right one to use on the negative pressure side of the pump!

 

[Best]

Thanks Best - I've just seen the video on the link you sent me. My Slovenian is not up to much, so I'll have spend some time on google translate to find out which bit of kit is the right one to use on the negative pressure side of the pump!

:smile: Yes, I knew it wasn't in English but it was the first video I came across & I thought it would do to show you. The Flamcovent model is the non painted brass model that slightly tapers to the top & has a little auto vent port at side. It could be got in 3/4" female threads or bigger. It is mainly for heating systems to catch air.
On your point about using a vent with a non return valve, - ideas ok but won't work.
I really can't rule out an ordinary auto vent, as it might work.
Do get the hot pipe to your shower fitted properly if you are ever redoing the work.

 

[DIY Bob]

Thanks for the information Best.

I might have a go at fitting an Aladdin HV30C auto air bleed valve on a verticle stub teed into the loft pipework.

The manufacturer's info says "you can use the HV30C on negative pressure systems. Their one–way valve makes them suitable for use .. on the suction side of the pump".

I've got one on the towel rail and it works fine. Just need to get hold of a 15mm to 1/2" BSP female adaptor to screw the Aladdin into.

I might as well give it a try. If it doesn't work, I haven't lost much! I'll let you know if it works, or if it sucks air into the power shower, or I just end up with a loft full of water...

 

[1Steven]

Hello Bob, just read your post. Am I reading correctly that both showers are off the same feed one pumped one not? If so you my get away with a single check valve fitted after the tee on the non pumped.

 

[DIY Bob]

Not quite Steven. Yes, both showers are fed off the same feed from the Surrey flange on the HW cylinder, but they are both pumped in different ways.

The feed to the main bathroom shower drops down to floor level adjacent to the HWC in the airing cupboard, through a shower pump, and into the bathroom. Quite conventional, no problems.

The feed to the en-suite bathroom goes up into the loft and back down to a Mira power shower, which obviously incorporates its own pump. That's the one that accumulates air over a period of time.

I can see that a non-return check valve into the feed to the ensuite might prevent water getting drawn back by the other pump, but wouldn't this also interfere with the water's ability to expand via the vent? I am not a plumber (just DIY) but I thought I've read in other threads that there are issues with fitting a check valve between a pumped circuit and the vent.

 

[1Steven]

You have the advantage of seeing the work laid out before you. I do hope you find a solutions regards, Steven

 

[DIY Bob]

Here's an update to my original issue, which was how to get rid of air accumulating in the up-and-over pipework to the power shower in my spare en-suite. In the long term, I know the pipework will need to be re-run under the floor, but I thought I'd try installing an Aladdin auto-vent in the loft. They claim to be one-way, suitable for installing in the 'suction' side of pumped systems, so I thought it was worth a try.

So I teed in a short vertical stub, with the auto-vent on top. I also fitted an iso valve in line, just in case it drew in air, or I had a leak.

The good news is that the auto-valve does not draw in air when the shower is in use. The bad news is that it doesn't seem to let air out of the system either! The air still accumulates in the pipework over a period of time, and I still have to manually purge it by running the shower for a few seconds with the shower handset held low.

I am a bit surprised that the Aladdin auto-vent is not letting the air out. The one on my towel rail works fine, so I've swapped them over just in case the new one is faulty. I'll let you know if it works.