vented mains pressure hot water flow problem

[action jackson]

Evening all.

I'm a regular user of the tiling forum but have popped over here to see if someone can help me work out what the problem is with my hot water flow issue? I have already had a plumber in but he is struggling to work out the problem.

I live in a first floor flat and believe i have a mains pressure, vented hot water system with 2 x electric immersion heaters. I'm by no means an expert but i believe the system consists of a water cylinder with internal coil, a separate header tank, an expansion vessel and a thermostatic mixing valve.

The issue i have is that the hot water flow has dropped off dramatically in the last couple of weeks, making it un-useable for running a bath or having a shower. Another issue that may be related is the header tank in the cylinder is continually overflowing and running through the overflow pipe. I haven't experienced this in the last 7 yrs.

About 2 months ago i had a whirlpool bath fitted with a concealed dornbrachet mixer unit and thermostatic control for bath and shower. No problems were experienced when initially installed.

The pressure in the expansion vessel was checked on Friday and was zero psi. I have pumped up to 1 bar and so far the pressure has remained stable, although it hasn't fixed the problem.

I was advised that maybe the thermostatic mixer valve for the shower/bath could be letting mains pressure pass into the hot water circuit due to the in balance with hot and cold? Is this possible and would this cause the water level in the cylinder to rise?

I should also add that the tank was removed 3 weeks ago because i though we had a crack in the cylinder, but we couldn't find any problems with the cylinder (blanked off and filled outside with cold water for 24 hours). We now think that the leak was actually coming from the overflow pipe in the header section of the cylinder which has now been fixed.

Lastly i recall checking the header part of the cylinder a couple of years ago and noticed it was bone dry! I wasn't sure why but as everything was working i didn't worry about it. (a guy at work is ex plumber and couldn't understand why i had a header tank in the cylinder for this type of system) Now the water is brimming out the top and continually overflowing!

Any sugestions or checks to carry out would be much welcomed! :icon4:

:icon4:

 

[ecowarm]

Agreed this is the easy route but at a cost. Best part of £1,000 for the cylinder and delivery. I'm not in a position to pay this much i'm afraid.

Google " Discount copper cylinders" in Manchester you may get the same thing cheaper there.

 

[MattWeth]

You can discharge an unvented cylinders' relief's into a soil pipe via a HepVo waterless trap (assuming as Gray0689 says, your cylinder is located near a soil pipe so you can route the discharge line with the correct fall).

 

[mikegas]

What is the minimum mains pressure for uvented systems? Mains pressure is not fantastic.

Ref copper discharge pipe to a safe point, what is required for an unvented install?

I live in a first floor flat and have no access to the outside etc.

1.5 bar and 20lpm min

 

[action jackson]

You can discharge an unvented cylinders' relief's into a soil pipe via a HepVo waterless trap (assuming as Gray0689 says, your cylinder is located near a soil pipe so you can route the discharge line with the correct fall).

I have decided i would like to go for a 170L direct UV gold cylinder from MR Central Heating. Before i do, can someone please advise if its possible to provide a suitable discharge as per the picture below of my current setup?

 

[MattWeth]

A discharge similar to your picture may be possible. There are several things to consider though (materials / pipe layout and arrangement etc) which really need the input of a plumber / heating engineer who is qualified on unvented hot water systems. However this type of discharge is not a preferred option and needs the explicit approval of your council building control department (there's no reason to suppose it wont be granted, but they must be consulted for approval).

 

[action jackson]

A discharge similar to your picture may be possible. There are several things to consider though (materials / pipe layout and arrangement etc) which really need the input of a plumber / heating engineer who is qualified on unvented hot water systems. However this type of discharge is not a preferred option and needs the explicit approval of your council building control department (there's no reason to suppose it wont be granted, but they must be consulted for approval).

Thanks. So my plumber has to get approval from the Building Council before he installs?

 

[dancinplumba]

I have decided i would like to go for a 170L direct UV gold cylinder from MR Central Heating. Before i do, can someone please advise if its possible to provide a suitable discharge as per the picture below of my current setup?

View attachment 5826

that pipework below hepvo is not of suitable material
imho

 

[action jackson]

that pipework below hepvo is not of suitable material
imho

can you suggest a suitable alternative method?

 

[dancinplumba]

your g3 certed plumber will be able to do that for you

 

[action jackson]

I will haveto find a new plumber as he is not registered.

In the meantimeI would like to go-ahead and order the cylinder as the supplier only delivers onTuesday’s and Thursday’s and I need to place the order today for Tuesdaydelivery.

Onlyproblem is I don’t have any to ask about the discharge pipe. I don’t need to know exact details butconfirmation that a discharge pipe should be possible with my setup would behelpful, as I can’t send the cylinder back.

 

[MattWeth]

I don't want to appear unhelpful or obstructive but you could really do with having an 'unvented qualified' plumber / heating engineer round to take a look before you order the cylinder. I and many others on here are qualified but it's hard for us to say what is or isn't possible or correct without seeing it in the flesh - it would be a nightmare if one of us said 'yes it'll be fine' and then you ordered the cyinder only to find that some detail we didn't know about rendered it impossible to fit.

Basically the cylinder will come with a 'kit of parts' including the safety devices and valves which the manufacturer has certified as appropriate for the cylinder. One of the big issues with an unvented cylinder is getting the relief valve discharges away from the tundish (supplied with the cylinder). This either has to go to an outside drain, a safe discharge onto the ground or in exceptional circumstances, directed back against a wall at high level or into a soil stack via a HepVo valve. These last two methods are classed as 'not preferred' and must have the prior approval of your council building control department.

Discharge into a soil stack must be in suitable high temperature waste pipes and via the HePvo vlave (the ribbed device below the tundish in your picture above). The pipework must also 'fall' at the correct rate to the connection to the soil stack.

Then you have to think about electrical and control requirements, making the necessary connections to the existing pipework and whether you have the necessary mains cold water pressure and flow to adequately serve an unvented hot water installation.

The above is just for starters. So you see it's not that straightforward and you really could do with getting someone who understands and is qualified inn unvented installations to take a look before you order. Bear in mind that the installation of an unvented hot water system is 'notifiable' (i.e. your council building control need to be informed) and that in all likelihood, you'll need prior approval for your relief valve discharge method. An unvented qualified plumber will be able to tell you whether it's possible and can sort all the building control liaison for you.

Matt

 

[dancinplumba]

put a post in the plumber or gas safe engineer thread, somone local on here may be able to help you out
imo

 

[action jackson]

Due to the regs it doesn't look like an unvented system is suitable for me, without a lot of costly work.

So i'm looking at a similar setup to what i already have (mains pressure thermal store twin immersion) and came accross this on ebay -

Range Flowmax Combi 180 thermal storage cylinder | eBay

Would it be possible to blank off the unused connections?

 

[dancinplumba]

yes not a problem
imo

 

[Dannypipe]

Ha - Its been stored dry in a barn for five years!! People are funny.

If you don't win it, try to negotiate a deal with a plumbers merchants. There are plenty of thermal stores on the market. You might get a bargain there though.

 

[ecowarm]

Looking at the pics on e bay that thermal store is not unused IMO

 

[tamz]

:iagree: with Eco. That cylinder has been fitted. You can see where the stat and banding have been and the labels are off as there would have been a date on it.
Probably mid 90's as the colour of the insulation changed to green around then.

 

[Gray0689]

Agree with Eco and tamz deffo used
Would not touch it

 

[action jackson]

Agree with Eco and tamz deffo used
Would not touch it

OK sounds like i will give it a miss then.

I have rang around but can't find one for less that £1,000 for a 170L twin immersion.

 

[Dannypipe]

Thermal stores aren't cheap.

Gledhill, BP model is about a grand or so.

I know a lot of people hate Gledhill, however their BP model isn't bad. I've fitted four of them.

That said, one has just had the immersion fail on it.

Gledhill cover the part under the warranty but not the labour, so I'll have to go change that for free. Also I have to send the old element back to them in order to get a refund.