Hot water & shower pump

[K4240]

Hi, I have a new shower but the hot water is intermittent.

It is a fixed shower head with a valve shower and I have a 2 bar shower pump. The pump is on the floor next to the hot water tank, which is below the cold water tank in the loft. The cold water tank, hot water tank and pump are all about 15-20m from the shower.

When I turn on the shower, in order to get the pump to start, I need to put it fully on cold water only. As I turn it to hot, the pump stops.

If I move it gradullay to hot, then as the hot starts to come through, the pump stays on, but often it will cut out again and I have to go back to just cold.

Help - I need a hot shower!!

Could this be the shower head? Or is it more serious (it's only been stalled for 5 months and only just started doing this)

Many thanks

 

[Richard C]

How far below the cws tank is the shower head mounted?
Where is the pipe run from the pump to the mixer i.e. do you have up & over pipe work from the pump into the loft & then back down to the mixer valve?
If yes do this pipes have vents at the highest point?
Do these pipes run below the level of the cws tank?
What make is the pump?

 

[K4240]

How far below the cws tank is the shower head mounted?
Shower head is on the ceiling of the upstairs bathroom and cold water tank is in loft, so only about 20cm, but cold water goes from the tank through the pump.


Where is the pipe run from the pump to the mixer i.e. do you have up & over pipe work from the pump into the loft & then back down to the mixer valve?
Yes - up and over

If yes do this pipes have vents at the highest point?
No - what type of vents?

Do these pipes run below the level of the cws tank?
Yes, just

What make is the pump?[/quote]
Salamdander

Does this help? Do I need to vent the pipes rather than a new shower head? How will this help?

Many thanks

 

[Richard C]

Which Salamander pump do you have? If you have a positive head pump, the minimum recommended distance for the shower head &/or delivery pipe work is 60 cm from the underside of the cws tank or you will be in a potentially negative head situation; this could be the cause of your problem

Up & over pipe work require vents fitted at the highest point otherwise air will accumulate in the loops & will eventually air lock the pump.

 

[K4240]

Which Salamander pump do you have? If you have a positive head pump, the minimum recommended distance for the shower head &/or delivery pipe work is 60 cm from the underside of the cws tank or you will be in a potentially negative head situation; this could be the cause of your problem

Up & over pipe work require vents fitted at the highest point otherwise air will accumulate in the loops & will eventually air lock the pump.

Not sure which pump it is, but it is more that 60cm below the cold tank.
The pump works fine when the shower is on cold only. It is when I start to turn it to hot that it cuts out. It is as though there is not enough hot flow to keep it running when the cold flow is reduced?

 

[Richard C]

Not sure which pump it is,

It's important to know which pump you have, look at the pump sticker!
Does it have a silver looking cylinder on the side of it?
Is it new or s/h?
Who installed it?

but it is more that 60cm below the cold tank.

I’ve already noted the pump is on the floor next to the hwc, that’s not what I asked you! If the shower head or any part of the pipe work (up & over loops) to the mixer is less than 60cm from the underside of the cws tank you could be in a negative head situation, if your not using a negative head or self selecting pump, you could have problems.

Who installed the pump?

The pump works fine when the shower is on cold only. It is when I start to turn it to hot that it cuts out. It is as though there is not enough hot flow to keep it running when the cold flow is reduced?

Aside from the above, it could be that you have a simple blockage in the hw feed from the pump (clean the strainers), faulty mixer valve or you may be air locked in the up & over h/w feed; these should be vented either manually, a pain as you have to keep bleeding them, or automatically using something like this;
http://www.screwfix.com/prods/97868/Plumbing/Brassware/Bottle-Air-Vent-15mm

 

[aceblade]

Hi Richard C how can I get a reply to my query here?

//www.diynot.com/diy/threads/negative-head-with-up-and-over-shower-pipework.422836/#3283417