Negative or positive shower pump

[Nat]

Hello all some help please,

I have fitted a shower pump upstairs in a two floor house. Pump is in the airing cupboard and is fed from a warix flange for the hot and has dedicated feed from the tank which is on a stolidge in the loft. The pipework goes upwards from the pump, along through the loft and then drops down to the shower valve inside a boxing at the head of the bath (there is a loop of pipework that goes down to below the top level of the bath and then back up again to the shower valve because the shower was originally teed off the bath tap supplies and this was the only way to connect it without breaking open the boxing).

All the pipework is below the level of the tank and there is 600mm below tank to shower head.

The shower pump stops working every couple of weeks and if I vent the pipe from pump to the shower bit of air comes out and it kicks in and starts working again.

Technical helpline say that I need a negative head pump but I thought this was only if the shower head was above the level of the tank?

Am I going to have to spend £300 on a new pump? That is going to hurt!

 

[REDSAW]

might need a gravity loop below the cylinder outlet and whats the head to pipes in loft?

 

[stevetheplumber]

i would check that the pump isnt drawing the cws tank down to the level of the cold feed to pump ,what you describe sounds fine and the fact it works most of the time shows theres enough flow to start the pump so your looking for some set of circumstance that occurs occasionally even a bit of dirt in the ball valve can slow tank fill below the output of the shower is it happening when the shower has been used more than at other times which would deplete the tank ,my daughter could empty a 50 gal tank on her own

 

[Whn1]

A couple of vents in the loft wouldn't hurt either.

 

[Nat]

might need a gravity loop below the cylinder outlet and whats the head to pipes in loft?

Thanks Redsaw. A gravity loop? Head is maybe 250mm

 

[Nat]

i would check that the pump isnt drawing the cws tank down to the level of the cold feed to pump ,what you describe sounds fine and the fact it works most of the time shows theres enough flow to start the pump so your looking for some set of circumstance that occurs occasionally even a bit of dirt in the ball valve can slow tank fill below the output of the shower is it happening when the shower has been used more than at other times which would deplete the tank ,my daughter could empty a 50 gal tank on her own

Thanks Steve. The thought that she is draining the tank had not occured to me. It is quite a big tank though.

 

[Nat]

A couple of vents in the loft wouldn't hurt either.

It did occur to me to put a couple of AAVs in there but that seems to not really be solving the problem.

 

[Nat]

Thanks Steve. The thought that she is draining the tank had not occured to me. It is quite a big tank though.

No I just called to check with her. It does not cut out after having a long shower. It works fine for a while then she'll go to turn it on and nothing happens. It seems airlocked to me as I have cut a couple of tees into the pipework from pump to shower in the loft with a couple of ballofix sticking up. As soon as I open up the ballofixes the pump springs into action and works fine. Turned it on and off a few times and all good.

Does no one think I SHOULD have a negative head pump as the Salamander Technical guy said?

 

[chris watkins]

Once again this shows that all these types of valves that promise air free hot water supplies to pumps do not work 100%.
If you don't what to re-pipe (look at the Mira suggested way) the cylinder take off, you could install a non latching pull-cord switch in the bathroom wired back to the pump, if the pump does not start due to air the customer pulls the cord the pump is momentarily started until the flow switch takes over. Simple but effective way to make your positive pump work.

 

[REDSAW]

it is a neg ed pump req

check it out here...

[DLMURL]http://designer-bathroom-taps.co.uk/Salamander%20Installation%20Guides/salamander-installation-guide.pdf[/DLMURL]

 

[Avatar]

Yes it is defiantly a negative head pump needed as likely the pressure is fluctuating from positive to negative.

Always follow the guidance of the tech support guys is your best bet!

 

[chris watkins]

Yes it is defiantly a negative head pump needed as likely the pressure is fluctuating from positive to negative.

Don't understand the above ???

 

[Avatar]

It might be 0.1 bar pressure when tested but once you open an outlet it switches to -0.1 bar or such like.

I had a job in a small hotel like this where they kept loosing water pressure on the highest floor of the property and it was a complete mystery why.

Tests showed positive pressure but I was advised that when a certain number of outlets were being used on the lower floors it it was possible that this may invert the pressure on the top floor into negative . . . .

Whole water system there was a mess and they baulked at a 15 grand Heatra Sadia system that would give them pressure a plenty!

Complicated? Maybe . . . .

 

[Nat]

I have seen a setup like what I have done in the salamander instructions that came with the pump. It shows using a couple of air vents like whn1 said above. I think I will give this.a go and if that does not work I will raise the tank a bit.