Advice needed for hot water feed to new shower pump

[Grundfos1]

I don't know if anyone is able to give me any advice regarding the supply of hot water to a shower pump.

Firstly I will point out that I have read a great deal on the subject I am just unsure how to proceed with my predicament, that's why I would be grateful for any advice.

I have a 50 gallon (well 2 x 25gallon) header tank in the loft, I have ensured that the float valve is in tank A and the supplies taken from tank B, there being 2 x 22mm feeds, 1 for the hot water cylinder in the airing cupboard, and one for the newly installed shower pump, also in the airing cupboard.
Unfortunately my hot water tank has a 3/4" tank connector on it so this rules out a Surry flange, instead I have used Warix Flange (as supplied by B&Q) to supply the hot water to the pump, unlike the Surry flanges the Warix flange has the shower pump outlet as the vertical one, while the DHW is fed from the horizontal feed.

The upshot is I am getting air in the shower pump feed, but only after the pump has been running for a good few minuets, and I am unsure how to proceed, the pump is a Grundfoss Niagra 2 bar twin impella one, mounted at the bottom of the hot water tank.

Will downsizing my pump to a 1.5 bar one, or should I say, one with less l/min demand help? or is this just delaying the problem, ie after 7 or 8 mins of operation?

Any help would be appreciated.

 

[seco services]

are you saying its draining your loft cws tank after 7 8 mins so drawing in air ?

 

[gas4you]

Personally I would have used an essex flange. No way it could suck air in on the hot then.

 

[Grundfos1]

No, sorry I should have been more specific, the cold water tanks are fine, they happily keep up with the demand, with hindsight there was no need for me to mention that part.

The sole problem is after running the pump for more than 3 to 4 mins with hot water required(not 100% hot water, just your average amount mixed with cold to have a suitable shower), the hot water starts to splutter and the pump gets noisier, after shutting it off for a few mins you can resume for another 3 to 4 mins.

if there is no hot water wanted (its a mixer valve) and only cold water is required the pump will happily go on all day.

 

[seco services]

what are you feeding the pump with from the cylinder 22mm or 15mm ?

 

[Grundfos1]

22mm all the way to within half a meter of the shower.

From hot water tank to pump is about 1/2 meter 22mm.
That's out of the Warix flange, into 22mm check valve, through 90 bend, then straight down into pump, all 22mm

Pump output 22mm for approx 3m, then 15mm reducer before going into a thermostatic mixer.

 

[seco services]

the pump is at the bottom of the cylinder you don't need a check valve in the hot supply.

 

[Grundfos1]

I just put one in so I can isolate the pump and clean the filers as and when.

 

[seco services]

are you talking about a isolation valve or check valve both different valves.

 

[Grundfos1]

Guess it would be an isolation valve, just called it a check valve as that's what it said on the diagram I was looking at.

 

[seco services]

have you a pic as thats could be half the problem.

 

[Grundfos1]

Hopefully there is a pic attached.

The plastic one on the left is for the shower pump, the copper one on the right is for the DHW.

I have put exactly the same stop valve in the cold water supply and there is no issue with that.

Untitled

• Grundfos1
• 2 Mar 2009
• 1

 

[seco services]

thats just a stop tap.
have you another pic covering pump, pipework etc ?

 

[Grundfos1]

Can get more pics tomorrow, but just after the cable tie you can see (only there ready to take the strain if the the pipe warps), there is a 90 degree bend, then straight down into the pump (although the pipe runs through a wooden battern just to hold it in place)

 

[mogget]

Untitled

• Grundfos1
• 2 Mar 2009
• 1

Where is the vent pipe for the cylinder?

I only see two pipes rising from the cylinder, and both have valves on them.

Also, what's the 'gunky' stuff on the far side of the gate valve?