Airlocks in hot water after fitting a surrey flange.

[JimHearne]

Hi all,
Sorry, this is a bit of a saga but I'm going to try and give all the details at the start.

How it was:

2 Storey house. Boiler on ground floor, indirect vented hot water cylinder on first floor, cold water tank sitting on the rafters in the loft.
One bathroom with just a bath (no shower), One en-suite with a thermostatic mixer shower (both hot and cold gravity feed), one downstairs loo with sink.
All hot water pipes run under the floors, nothing goes up and through the loft except the separate gravity cold water feed for the en-suite shower which goes from the cold water tank directly down to the shower.
Mains water pressure 6.5bar.
Somewhere under the floor between the hot water cylinder and the bathroom the pipe goes from 22mm to 15mm.
Hot water cylinder is about 3m from the bathroom and I'm pretty sure the pipes carry on from there to the en-suite under the floor still.
No problems apart from the thermostatic en-suite shower being quite fussy about doing warm, it tends to either do hot or cold and whistle at the switchover, I put this down to the low gravity water pressure.

Anyway, we decided to replace the standard bath in the main bathroom with a shower bath with the shower feed from mixer taps.
After this was all done we realised that that the cold water in this bathroom was mains pressure and the hot water was only gravity, so the slightest opening of the cold water tap just stopped the hot water (and probably forced cold water back into the hot).

Did a lot of reading on the net, and realised that without ripping out the newly fitted bath and tiles to take up the laminate floor and floor boards, and run in new pipes, that the only option was to fit a pump on the hot water to try and match the pressure of the cold water.
I know there will be some here that will say that's not a good idea, or it won't work, but I did consult with a pump supplier first, and it does seem to work, it's not the actual problem I'm having.

Anyway, got a pump ( Stuart Turner Showermate U2.6Bar Single 46534) and fitted it to the feed to the bath hot water tap, actually under the end of the bath.
Fitted a pressure regulator to the mains cold water feed to the bath cold tap to drop that down to about 2.6 bar as well.

I'd read about the problems of sucking air in from the vent with the pump so I fitted a Surrey flange to the top of the hot water tank.

The original setup just had the hot water outlet coming out of the top of the tank, 90 degree bend to horizontal, across to the side of the tank, then a T with the vent pipe going straight up to the loft and the hot water outlet going straight down under the floor.

My first attempt with the Surrey flange had the side outlet from the Surrey flange going horizontally across and then 90 degrees down into the original outlet pipe.
The top outlet from the Surrey flange went straight into a 90 degree bend, across horizontally (maybe a little down hill after all soldered up) and then another 90 degree bend to go up onto the original vent pipe.
I know this isn't quite normal as usually you would only have the feed for a shower pump from the Surrey flange but I couldn't find or think of any reason why it would cause problems having all the hot water going through it.
The pump seems to run quite happily but we've not been using it at all yet as the shower screen etc still needs fitting.

So, this was all done (not using the pumped shower at all) but after a couple of days the hot water pressure at the en-suite shower dropped right away, so that in the end it barely trickled out.
The water pressure at the other hot taps seemed to have dropped as well, even those downstairs.
After some messing about with taps and then switching on the pump for a min or so it seemed to suck some air through (I know this is very bad for them), and all the pressures were back to normal at the other shower and taps.

But the problem re-occurred every couple of days, needing the pump (which we weren't using otherwise) to be turned on to seemingly suck air out of the system to fix it.
I thought maybe the problem was air being trapped in the 2 horizontal pipes I had above the cylinder (the outlet and vent) so I removed them all and replaced the vent pipe with a section going up at 45 degrees to the vertical pipe.
And the hot water outlet pipe I replaced with a curved pipe I bent to a bit bigger radius than the cylinder so there was minimal horizontal section.

But, the airlock problems remain.

The Surrey flange I have seems to have a small rubber vent with a small hole in it between the outlet and the vent sections, I assume so any small amount of air that does get stuck in the outlet pip can still escape into the vent pipe.

When the hot water looses pressure water can be heard running in the outlet pipe from the cylinder, when there is normal pressure you can't hear this.
The vent pipe is hot and gradually gets cooler the higher you go (but still hot up to the ceiling), the end of the pipe above the cold water tank is above the water surface.

I can't figure out where the air is getting into the system, fitting the Surrey flange seems to have created a problem we didn't have before.

I can take some pictures of the pipework around the cylinder tomorrow.

If you have read this far, any thoughts please ?

Many thanks,

Jim

 

[Toxic Ted]

I think i need glasses after reading that

 

[thompsonbrown]

Sounds like you are pulling air in from somewhere but reading the spec on the shower, as below

The Showermate Universal 2.6 bar Single pump is designed to improve water supplies to single taps or to pump blended water from a shower mixer in negative head plumbing systems.

It could also be the wrong pump? single taps or blended water to me does not say hot supply to shower mixer.

Its hard to say exactly what the problem is but if you could exchange the pump you could always fit a stuart turner Monsoon whole house pump next to the cylinder and pressurize all hot water outlets. you would have to check what differential pressures your gravity shower will work with

 

[lame plumber]

surrey flange probably installed wrong , pipe sloping wrong way etc etc. would have been simpler to convert cold supply back to tank fed! long term convert whole cyl to unvented with balanced supply and problems should all go away. why not get a decent plumber in to look at what youve got there and suggest remedies.

 

[JimHearne]

Sounds like you are pulling air in from somewhere but reading the spec on the shower, as below

The Showermate Universal 2.6 bar Single pump is designed to improve water supplies to single taps or to pump blended water from a shower mixer in negative head plumbing systems.

It could also be the wrong pump? single taps or blended water to me does not say hot supply to shower mixer.

Its hard to say exactly what the problem is but if you could exchange the pump you could always fit a stuart turner Monsoon whole house pump next to the cylinder and pressurize all hot water outlets. you would have to check what differential pressures your gravity shower will work with

Hi, thanks for the reply.
The pump was the one recommended by Stuart-Turner themselves after I gave them all the details above so should be correct.
But, the pump isn't causing the problem, as I said, it's not being used yet.
I did consider pressurising the entire hot water system but then I would have to have to change the feed to the gravity shower and the only mains pressure feed in the loft is a 15mm one to the cold water tank, I didn't think that would be big enough.

Many thanks,

Jim

 

[JimHearne]

surrey flange probably installed wrong , pipe sloping wrong way etc etc. would have been simpler to convert cold supply back to tank fed! long term convert whole cyl to unvented with balanced supply and problems should all go away. why not get a decent plumber in to look at what youve got there and suggest remedies.

Hi, thanks for the reply.

I did consider converting the bath back to a gravity feed but to be honest with the cold water tank on the rafters there isn't much pressure, and also, to get the new feed to the bath would have meant removing the newly fitted bath and tiles around it.
Long term I may consider a unvented system, especially as fitting the surrey flange created a few pinholes around the top of the tank, presumably from corrosion inside. These are currently sealed with LSX but i'm keeping an eye on it.
I understand how the surrey flange works so not quite sure how it could be fitted wrong apart from mixing up the 2 pipes.
Any air in the tank collects at the top and exits via the top connection on the Surrey flange, The hot water is drawn from the side outlet on the flange which goes down inside the tank 6" so it can't (shouldn't) be able to suck in any air.

Many thanks,

Jim

 

[Best]

Hope you didn't fit a Warix flange thinking it is a Surrey flange? Pipe connections are the opposite. :smile:

 

[JimHearne]

Hope you didn't fit a Warix flange thinking it is a Surrey flange? Pipe connections are the opposite. :smile:

I don't think so, you could see straight through the top of the fitting around the centre pipe.
And the side outlet curves round 90 degrees and goes down the centre pipe.

Thanks,

Jim

 

[Best]

You maybe better check all connections at flange & pump incase air is being sucked in somewhere. Also check the vent pipe isn't sticking down into the water in the cold tank.
Sounds baffling.

 

[JimHearne]

You maybe better check all connections at flange & pump incase air is being sucked in somewhere. Also check the vent pipe isn't sticking down into the water in the cold tank.
Sounds baffling.

Wouldn't water leak out if air can get in ?
The pump isn't being used yet so it's not that the pump is sucking air in.

I will double check the vent pipe but it was well above the water before I soldered everything up and should be in the same place as I marked the height of the vent pipe inside the airing cupboard.

It's certainly baffling me.

Many thanks,

Jim

 

[Best]

Yes Jim, you would probably have small leaks showing, but wouldn't take much air to be drawn in to cause airlock. If it is easy & nothing else obvious, why not try doing away with flange to test?

 

[Phil_Plumb]

did you fit a salamander s type flange? if so may worth removing flange to see if this helps, if not may have to consider fitting an essex flange to the side of the cylinder!

 

[JimHearne]

did you fit a salamander s type flange? if so may worth removing flange to see if this helps, if not may have to consider fitting an essex flange to the side of the cylinder!

It was one of these which is similar but I believe is a Surrey flange:



Unfortunately after the pinholes that appeared around the boss In the tank after the flange being fitted twice so far, I think taking it off again will need a new tank.

Many thanks,

Jim

 

[happyflyer]

I think i need glasses after reading that

counselling

 

[Phil_Plumb]

does it look like that when out of the packet! if so thats a Salamander Surrey Flange.

You may want to consider fitting an essex flange - as these sit about half way down the tank, therefore way below the water level and any air pockets that may be there!

 

[JimHearne]

does it look like that when out of the packet! if so thats a Salamander Surrey Flange.

You may want to consider fitting an essex flange - as these sit about half way down the tank, therefore way below the water level and any air pockets that may be there!

Very similar, it looks like this.
Same idea, any air bubbles rising up can't get into the centre outlet.

The tank should be full of water, as should the vent pipe up to the level of the water in the cold water tank.
So I can't see that the Essex flange would work any differently to this one ?

Many thanks,

Jim

 

[Phil_Plumb]

yes in theory and practice thats how a surrey flange works, the dip tube sits a little further down into the tank and therefor the tip with the holes in it should be submersed by the water. How ever if its still not working or doing as it should be designed and air is still getting in then an essex flange can be used.

They require a whole to be drilled on side of cylinder, chip a way a square (bigger than the fitting) of insulation, and clean up exposed copper. install flange through immersion heater hole.

By putting the pump feed pipe lower down the tank you are gaurunteeing the feed to be almost if not completely air bubble free as the water level will be way above toward top of tank.

If you have checked everywhere else for a leak and or air admittance, and you have narrowed it down to that flange, have you taken it back for a replacement to rule out a faulty a faulty fitting, if not take it back and ask for a Salamander S type flange. it should be identical to the one in the pic i posted up!

 

[Plum Bob 66]

Any chance you could send us over those snaps of the pipe work layout from the cylinder, you never know something might be gleaned from the images.

 

[JimHearne]

Any chance you could send us over those snaps of the pipe work layout from the cylinder, you never know something might be gleaned from the images.

There are pictures of my first version, I've drawn the current version on in one picture in blue lines.
The other picture shows the original pipework in red before the Surrey flange was fitted.



Many thanks,

Jim

 

[PlumbBobBob]

well that's your problem. even though you have separate hot feed and vent pipes they still need to be joined together to allow any air to be vented out.

 

[Plum Bob 66]

There we go, and easy to remedy Jim.

 

[Plum Bob 66]

Don't think we cottoned on to the fact that you plumbed the whole house hot feed into the flange without joining the vent at some stage. In most flange applications I have come across the lower fitting has been the dedicated hot feed to the shower and the top feeds the rest of the hot circuit and t ed into the vent.

 

[JimHearne]

well that's your problem. even though you have separate hot feed and vent pipes they still need to be joined together to allow any air to be vented out.

Hi Steve,
Are you saying I need to link the 2 vertical pipes ?, using 2 T's where the angles are at the moment.

If so, I'm afraid I don't understand.

Isn't one of the reasons for using the Surrey flange so that when the pump is running it doesn't suck all the water down out of the vent pipe and suck in air ?
With the 2 pipes linked again it can still do that can't it ?

Many thanks for you advice,

Jim

 

[lame plumber]

should be like this

 

[JimHearne]

Don't think we cottoned on to the fact that you plumbed the whole house hot feed into the flange without joining the vent at some stage. In most flange applications I have come across the lower fitting has been the dedicated hot feed to the shower and the top feeds the rest of the hot circuit and t ed into the vent.

I obviously didn't give enough information in the first message

I still don't fully understand.
If I fitted the pump in the airing cupboard so all the hot water in the house was pumped then the side outlet of the Surrey flange would go to the pump only and the top outlet would go to the vent only ?

Many thanks,

Jim

 

[JimHearne]

should be like this

Hi, that has a separate outlet for the pump, I can't do that without ripping up floors.
But, I now have all the hot water connected to where the pump is in that diagram, with the pump just on the bath mixer tap, why is that different to that setup in terms off venting air.
I'm obviously missing something.

Thanks,

Jim

 

[lame plumber]

do as the guys say or youll never get it working, let it b one of lifes little mysteries

 

[JimHearne]

I don't like mysteries, I like to understand.

Jim

 

[secret squirrel]

Can you isolate the shower on the bath?

Not use it for a couple of days and see it the problem persists,

Then if the problem persists isolate something else?

I do see your point about the flange, TBH I did your set up to cure a pump problem, it worked, pump was working on the shower but fitted incorrectly, it was my only option.

There is a valve you can buy, I can't remember what its called, its like a one way check valve but not quite, a butterfly type of valve, I dealt with a problem similar to yours and the manufacturer sent me the valves, again worked a treat.

Could it be a faulty mixer tap and the cold is passing through the to the hot (hence isolate everything in sequence), TMV have been known to create problems.

 

[lame plumber]

There are pictures of my first version, I've drawn the current version on in one picture in blue lines.
The other picture shows the original pipework in red before the Surrey flange was fitted.

View attachment 13602 View attachment 13603

Many thanks,

Jim

the reason for the problem is here squirrel

 

[JimHearne]

Can you isolate the shower on the bath?

Not use it for a couple of days and see it the problem persists,

Then if the problem persists isolate something else?

I do see your point about the flange, TBH I did your set up to cure a pump problem, it worked, pump was working on the shower but fitted incorrectly, it was my only option.

There is a valve you can buy, I can't remember what its called, its like a one way check valve but not quite, a butterfly type of valve, I dealt with a problem similar to yours and the manufacturer sent me the valves, again worked a treat.

Could it be a faulty mixer tap and the cold is passing through the to the hot (hence isolate everything in sequence), TMV have been known to create problems.

I can isolate the shower on the bath but the shower and bath (and pump) are not being used as yet.
Still, the pipework under the bath is pushfit plastic and I've some blanking caps I can fit easily enough.

Where in the pipework did you fit the butterfly valve ?

Many thanks,

Jim

 

[secret squirrel]

On the pump. both outlets, as something was turned off it did something and created an issue, I can't really remember all the ins and outs of the saga, it was a job I inherited and was glad to see the back of it!

I am almost sure it was air problems. but the valves can only help cure a potential issue.

It was on a showermate pump, I got lost reading your original post TBH.

 

[secret squirrel]

the reason for the problem is here squirrel

I don't disagree with what anyone is saying here at all, I've done what the OP has done, albeit the pump was still only working the shower, it cured the issue the customers poor installation.

Just a different view.

If someone has a whole house pump....... I'm too tired to have a chat about this really.

 

[lame plumber]

, it cured the customers poor installation... I'm too tired to have a chat about this really.

you said it all really, been a long day with me as well

 

[Plum Bob 66]

IMO Jim you would be better off capping the top outlet of the flange and t ing hot outlet into the expansion pipe. Pretty much leaving you as you were before the flange was fitted but with bonus of air free hot water, bet that solves your problem.